diff --git a/include/youprop.h b/include/youprop.h
index fa85420cf..905012516 100644
--- a/include/youprop.h
+++ b/include/youprop.h
@@ -290,6 +290,20 @@
 #define EHalf_spell_damage	u.uprops[HALF_SPDAM].extrinsic
 #define Half_spell_damage	(HHalf_spell_damage || EHalf_spell_damage)
 
+/*
+ * Physical damage
+ *
+ * Damage is NOT physical damage if (in order of priority):
+ * 1. it already qualifies for some other special category
+ *    for which a special resistance already exists in the game 
+ *    including: cold, fire, shock, acid, and magic.
+ *    Note that fire is extended to include all non-acid forms of
+ *    burning, even boiling water since that is already dealt with
+ *    by fire resistance, and in most or all cases is caused by fire. 
+ * 2. it doesn't leave a mark. Marks include destruction of, or 
+ *    damage to, an internal organ (including the brain), 
+ *    lacerations, bruises, crushed body parts, bleeding.
+ */
 #define HHalf_physical_damage	u.uprops[HALF_PHDAM].intrinsic
 #define EHalf_physical_damage	u.uprops[HALF_PHDAM].extrinsic
 #define Half_physical_damage	(HHalf_physical_damage || EHalf_physical_damage)
diff --git a/src/detect.c b/src/detect.c
index 1a6cc4890..7ed39726a 100644
--- a/src/detect.c
+++ b/src/detect.c
@@ -820,6 +820,7 @@ struct obj *obj;
 	case 5 : pline("%s!", Tobjnam(obj, "explode"));
 	    useup(obj);
 	    obj = 0;	/* it's gone */
+	    /* physical damage cause by the shards and force */
 	    losehp(Maybe_Half_Phys(rnd(30)),
 			"exploding crystal ball", KILLED_BY_AN);
 	    break;
diff --git a/src/do.c b/src/do.c
index 46e4e9027..0031e62a5 100644
--- a/src/do.c
+++ b/src/do.c
@@ -102,7 +102,7 @@ boolean pushing;
 			Fire_resistance ? '.' : '!');
 			burn_away_slime();
 		    dmg = d((Fire_resistance ? 1 : 3), 6);
-		    losehp(Maybe_Half_Phys(dmg),
+		    losehp(Maybe_Half_Phys(dmg),	/* lava damage */
 			   "molten lava", KILLED_BY);
 		} else if (!fills_up && flags.verbose &&
 			   (pushing ? !Blind : cansee(rx,ry)))
diff --git a/src/eat.c b/src/eat.c
index 347e8b13c..453ac7f74 100644
--- a/src/eat.c
+++ b/src/eat.c
@@ -1260,7 +1260,7 @@ eatcorpse(otmp)		/* called when a corpse is selected as food */
 	} else if (acidic(&mons[mnum]) && !Acid_resistance) {
 		tp++;
 		You("have a very bad case of stomach acid."); /* not body_part() */
-		losehp(Maybe_Half_Phys(rnd(15)), "acidic corpse", KILLED_BY_AN);
+		losehp(rnd(15), "acidic corpse", KILLED_BY_AN); /* acid damage */
 	} else if (poisonous(&mons[mnum]) && rn2(5)) {
 		tp++;
 		pline("Ecch - that must have been poisonous!");
diff --git a/src/explode.c b/src/explode.c
index e7d687954..c0d707bec 100644
--- a/src/explode.c
+++ b/src/explode.c
@@ -71,8 +71,8 @@ int expltype;
 		case 1: str =   olet == BURNING_OIL ?	"burning oil" :
 				olet == SCROLL_CLASS ?	"tower of flame" :
 							"fireball";
+			/* fire damage, not physical damage */
 			adtyp = AD_FIRE;
-			physical_dmg = TRUE;
 			break;
 		case 2: str = "ball of cold";
 			adtyp = AD_COLD;
diff --git a/src/fountain.c b/src/fountain.c
index 366aa25c6..6cc8c1a5d 100644
--- a/src/fountain.c
+++ b/src/fountain.c
@@ -524,8 +524,8 @@ drinksink()
 		case 2: You("take a sip of scalding hot water.");
 			if (Fire_resistance)
 				pline("It seems quite tasty.");
-			else losehp(Maybe_Half_Phys(rnd(6)),
-					"sipping boiling water", KILLED_BY);
+			else losehp(rnd(6), "sipping boiling water", KILLED_BY);
+				/* boiling water burns considered fire damage */
 			break;
 		case 3: if (mvitals[PM_SEWER_RAT].mvflags & G_GONE)
 				pline_The("sink seems quite dirty.");
diff --git a/src/mcastu.c b/src/mcastu.c
index 2b2c91a50..24ea19ad6 100644
--- a/src/mcastu.c
+++ b/src/mcastu.c
@@ -484,7 +484,9 @@ int spellnum;
 
     switch (spellnum) {
     case CLC_GEYSER:
-	/* this is physical damage, not magical damage */
+	/* this is physical damage (force not heat),
+	 * not magical damage or fire damage
+	 */
 	pline("A sudden geyser slams into you from nowhere!");
 	dmg = d(8, 6);
 	if (Half_physical_damage) dmg = (dmg + 1) / 2;
diff --git a/src/mhitu.c b/src/mhitu.c
index 4dba6b387..fd74ff565 100644
--- a/src/mhitu.c
+++ b/src/mhitu.c
@@ -1783,6 +1783,8 @@ register struct monst *mtmp;
 register struct attack  *mattk;
 boolean ufound;
 {
+    boolean physical_damage = TRUE;
+
     if (mtmp->mcan) return(0);
 
     if (!ufound)
@@ -1798,12 +1800,15 @@ boolean ufound;
 
 	switch (mattk->adtyp) {
 	    case AD_COLD:
+	        physical_damage = FALSE;
 		not_affected |= Cold_resistance;
 		goto common;
 	    case AD_FIRE:
+	        physical_damage = FALSE;
 		not_affected |= Fire_resistance;
 		goto common;
 	    case AD_ELEC:
+	        physical_damage = FALSE;
 		not_affected |= Shock_resistance;
 common:
 
@@ -1815,7 +1820,7 @@ common:
 		        if (flags.verbose) You("get blasted!");
 		    }
 		    if (mattk->adtyp == AD_FIRE) burn_away_slime();
-		    if (Half_physical_damage) tmp = (tmp+1) / 2;
+		    if (physical_damage) tmp = Maybe_Half_Phys(tmp);
 		    mdamageu(mtmp, tmp);
 		}
 		break;
diff --git a/src/mon.c b/src/mon.c
index 21894887e..f5d73d97a 100644
--- a/src/mon.c
+++ b/src/mon.c
@@ -2012,7 +2012,7 @@ int  typ, fatal;
 		    pline("You%s!", poiseff[typ]);
 	} else {
 		i = thrown_weapon ? rnd(6) : rn1(10,6);
-		losehp(Maybe_Half_Phys(i), pname, kprefix);
+		losehp(i, pname, kprefix); /* poison damage */
 	}
 	if(u.uhp < 1) {
 		killer.format = kprefix;
diff --git a/src/mthrowu.c b/src/mthrowu.c
index a6501d5aa..0c0af1dfe 100644
--- a/src/mthrowu.c
+++ b/src/mthrowu.c
@@ -73,7 +73,7 @@ const char *name;	/* if null, then format `obj' */
 			pline("It doesn't seem to hurt you.");
 		else {
 			if (is_acid) pline("It burns!");
-			losehp(Maybe_Half_Phys(dam), knm, kprefix);
+			losehp(dam, knm, kprefix);	/* acid damage */
 			exercise(A_STR, FALSE);
 		}
 		return(1);
diff --git a/src/music.c b/src/music.c
index b661816ec..d3ba97e49 100644
--- a/src/music.c
+++ b/src/music.c
@@ -355,7 +355,6 @@ do_improvisation(instr)
 struct obj *instr;
 {
 	int damage, do_spec = !Confusion;
-	boolean physical_damage = FALSE;
 #if defined(MAC) || defined(AMIGA) || defined(VPIX_MUSIC) || defined (PCMUSIC)
 	struct obj itmp;
 
@@ -400,8 +399,6 @@ struct obj *instr;
 	    exercise(A_DEX, TRUE);
 	    break;
 	case FIRE_HORN:			/* Idem wand of fire */
-	    physical_damage = TRUE;
-	    /* fall through */
 	case FROST_HORN:		/* Idem wand of cold */
 	    if (do_spec && instr->spe > 0) {
 		consume_obj_charge(instr, TRUE);
@@ -413,8 +410,8 @@ struct obj *instr;
 		    if ((damage = zapyourself(instr, TRUE)) != 0) {
 			char buf[BUFSZ];
 			Sprintf(buf, "using a magical horn on %sself", uhim());
-			if (physical_damage) damage = Maybe_Half_Phys(damage);
-			losehp(damage, buf, KILLED_BY);
+			losehp(damage, buf, KILLED_BY); /* frost damage */
+							/* fire damage */
 		    }
 		} else {
 		    buzz((instr->otyp == FROST_HORN) ? AD_COLD-1 : AD_FIRE-1,
diff --git a/src/potion.c b/src/potion.c
index ae4adec62..5c1dff265 100644
--- a/src/potion.c
+++ b/src/potion.c
@@ -879,7 +879,8 @@ peffects(otmp)
 				good_for_you = TRUE;
 			    } else {
 				You("burn your %s.", body_part(FACE));
-				losehp(Maybe_Half_Phys(d(Fire_resistance ? 1 : 3, 4)),
+				/* fire damage */
+				losehp(d(Fire_resistance ? 1 : 3, 4),
 				       "burning potion of oil", KILLED_BY_AN);
 			    }
 			} else if(otmp->cursed)
@@ -1683,7 +1684,7 @@ dodip()
 				potionbreathe(obj);
 			useup(obj);
 			useup(potion);
-			losehp(Maybe_Half_Phys(rnd(10)), "alchemic blast",
+			losehp(rnd(10), "alchemic blast",  /* not physical damage */
 					KILLED_BY_AN);
 			return(1);
 		}
diff --git a/src/read.c b/src/read.c
index a93e0bc50..f324b2d71 100644
--- a/src/read.c
+++ b/src/read.c
@@ -1143,8 +1143,7 @@ register struct obj	*sobj;
 		    } else {
 			pline_The("scroll catches fire and you burn your %s.",
 				makeplural(body_part(HAND)));
-			losehp(Half_physical_damage ? rn2(2) : 1,
-				"scroll of fire", KILLED_BY_AN);
+			losehp(1, "scroll of fire", KILLED_BY_AN);
 		    }
 		    return(1);
 		}
diff --git a/src/sit.c b/src/sit.c
index 69c4f90f1..4104fb6c7 100644
--- a/src/sit.c
+++ b/src/sit.c
@@ -92,7 +92,7 @@ dosit()
 		    /* Must have fire resistance or they'd be dead already */
 		    You("sit in the lava!");
 		    u.utrap += rnd(4);
-		    losehp(Maybe_Half_Phys(d(2,10)), "sitting in lava", KILLED_BY);
+		    losehp(d(2,10), "sitting in lava", KILLED_BY); /* lava damage */
 		} else if(u.utraptype == TT_INFLOOR || u.utraptype == TT_BURIEDBALL) {
 		    You_cant("maneuver to sit!");
 		    u.utrap++;
@@ -146,7 +146,7 @@ dosit()
 		return 1;
 	    }
 	    pline_The("lava burns you!");
-	    losehp(Maybe_Half_Phys(d((Fire_resistance ? 2 : 10), 10)),
+	    losehp(d((Fire_resistance ? 2 : 10), 10),	/* lava damage */
 		   "sitting on lava", KILLED_BY);
 
 	} else if (is_ice(u.ux, u.uy)) {
diff --git a/src/spell.c b/src/spell.c
index 59cbd5de8..5828b8532 100644
--- a/src/spell.c
+++ b/src/spell.c
@@ -837,8 +837,6 @@ boolean atme;
 	 * additional cost to the spellcaster.
 	 */
 	case SPE_FIREBALL:
-	    physical_damage = TRUE;
-	    /* fall through */
 	case SPE_CONE_OF_COLD:
 	    if (role_skill >= P_SKILLED) {
 	        if (throwspell()) {
@@ -849,8 +847,6 @@ boolean atme;
 			    if ((damage = zapyourself(pseudo, TRUE)) != 0) {
 				char buf[BUFSZ];
 				Sprintf(buf, "zapped %sself with a spell", uhim());
-				if (physical_damage)
-					damage = Maybe_Half_Phys(damage);
 				losehp(damage, buf, NO_KILLER_PREFIX);
 			    }
 			} else {
diff --git a/src/trap.c b/src/trap.c
index 0abeccd27..2084e93a0 100644
--- a/src/trap.c
+++ b/src/trap.c
@@ -2413,7 +2413,7 @@ struct obj *box;	/* null for floor trap */
 	    pline("A cascade of steamy bubbles erupts from %s!",
 		    the(box ? xname(box) : surface(u.ux,u.uy)));
 	    if (Fire_resistance) You("are uninjured.");
-	    else losehp(Maybe_Half_Phys(rnd(3)), "boiling water", KILLED_BY);
+	    else losehp(rnd(3), "boiling water", KILLED_BY);
 	    return;
 	}
 	pline("A %s %s from %s!", tower_of_flame,
@@ -2442,7 +2442,7 @@ struct obj *box;	/* null for floor trap */
 	if (!num)
 	    You("are uninjured.");
 	else
-	    losehp(Maybe_Half_Phys(num), tower_of_flame, KILLED_BY_AN);
+	    losehp(num, tower_of_flame, KILLED_BY_AN);	/* fire damage */
 	burn_away_slime();
 
 	if (burnarmor(&youmonst) || rn2(3)) {
@@ -3898,7 +3898,7 @@ lava_effects()
 	    dmg = d(6,6);
 	    pline_The("lava here burns you!");
 	    if(dmg < u.uhp) {
-		losehp(Maybe_Half_Phys(dmg), lava_killer, KILLED_BY);
+		losehp(dmg, lava_killer, KILLED_BY);	/* lava damage */
 		goto burn_stuff;
 	    }
 	} else
@@ -3955,7 +3955,7 @@ lava_effects()
 	u.utraptype = TT_LAVA;
 	You("sink into the lava, but it only burns slightly!");
 	if (u.uhp > 1)
-	    losehp(Half_physical_damage ? rn2(2) : 1, lava_killer, KILLED_BY);
+	    losehp(1, lava_killer, KILLED_BY);	/* lava damage */
     }
     /* just want to burn boots, not all armor; destroy_item doesn't work on
        armor anyway */
diff --git a/src/uhitm.c b/src/uhitm.c
index a9d431f3f..6f115ba85 100644
--- a/src/uhitm.c
+++ b/src/uhitm.c
@@ -2324,7 +2324,7 @@ uchar aatyp;
 			break;
 		    }
 		    You("are suddenly very hot!");
-		    mdamageu(mon, Maybe_Half_Phys(tmp));
+		    mdamageu(mon, tmp);		/* fire damage */
 		}
 		break;
 	      case AD_ELEC:
diff --git a/src/zap.c b/src/zap.c
index db8e8385e..63589ae24 100644
--- a/src/zap.c
+++ b/src/zap.c
@@ -3862,7 +3862,6 @@ register int osym, dmgtyp;
 		    break;
 		case AD_FIRE:
 		    xresist = (Fire_resistance && obj->oclass != POTION_CLASS);
-		    physical_damage = TRUE;
 
 		    if (obj->otyp == SCR_FIRE || obj->otyp == SPE_FIREBALL)
 			skip++;