I sometimes see or hear pairs of these words confused.

Problem:
These four verbs are not synonyms.

Explanation:
I was watching an episode of the Fox TV show “Fringe”, which included some FBI agents chasing a bad guy.

One actor seemed to say “alluded” — spelled A-L-L-U-D-E-D — when telling another actor that the bad guy had escaped.

The verb “allude”, which dates back to the early 1500s and is spelled A-L-L-U-D-E, means to refer indirectly or casually. This verb comes from the Latin verb “alludere” (to play beside), from “al-” (toward) and “ludere” (to play).

What the actor should have said instead was “eluded” — spelled E-L-U-D-E-D — when referring to the bad guy’s escape.

The verb “elude”, which dates back to the mid-1500s and is spelled E-L-U-D-E, means to escape or avoid by trickery, cleverness, or speed. This verb comes from the Latin verb “eludere” (to evade or deceive), from “e-” (out of, from, or beyond) and “ludere” (to play).

I believe that many English speakers tend to pronounce “allude” and “elude” identically as “uh-lude”.

This is a mistake. The solution is to pronounce the “al” in “allude” in just the same way that one should pronounce the “al” in “allegory”, and to pronounce the “e” in “elude” in just the same way that one should pronounce the “e” in “email”.

Some people confuse the verb “elude” with the verb “delude”, perhaps because these two words differ by only one letter.

The verb “delude”, which dates back to the early 1400s and is spelled D-E-L-U-D-E, means to mislead the judgment or mind of. This verb comes from the Latin verb “deludere” (to play false), from “de-” (down) and “ludere” (to play).

Finally, the verb “illude”, which dates back to the mid-1400s and is spelled I-L-L-U-D-E, means to trick or deceive. This verb comes from the Latin verb “illudere” (to ridicule or mock), from “il-” (in) and “ludere” (to play).

I sometimes see or hear “illude” and “delude” used interchangeably, apparently because writers or speakers see “ill”, which looks negative and therefore somewhat like “de”, instead of “il”, which is the actual prefix of “illude” and is simply a variation of “in”.

The verbs “illude” and “delude” are not quite synonyms. Although both verbs generically mean to deceive, the verb “delude” is more about unconscious or unintentional misleading, especially reflexively, whereas the verb “illude” is more about conscious or intentional trickery.

Solution:

• Use “allude” when one means to refer indirectly or casually.
• Use “delude” when one means to mislead the judgment or mind of. The verb “delude” is often used reflexively.
• Use “elude” when one means to escape or avoid by trickery, cleverness, or speed.
• Use “illude” when one means to trick or deceive.