My wife heard the first word used several times yesterday as a synonym of the second word, and I once worked for someone who regularly made the same mistake.

Problem:
These two words are not synonyms.

Explanation:
The word “simular” — spelled S-I-M-U-L-A-R — dates back to the early 1500s.

The meaning of “simular” as a noun is pretender. The primary meaning of “simular” as an adjective is simulated or counterfeit.

A valid example of the use of “simular” as an adjective would be “Pleather is simular leather.”

The word “similar” — spelled S-I-M-I-L-A-R — dates back to the early 1600s, is only an adjective, and primarily means having a resemblance or likeness.

A valid example of the use of “similar” as an adjective would be “The two automobiles in the parking lot were so similar that John tried to unlock the wrong one.”

I believe that some people mispronounce and/or misspell the adjective “similar” — spelled S-I-M-I-L-A-R — as “simular” — spelled S-I-M-U-L-A-R — because of interference from the verb “simulate”, which does have the vowel “u” in the middle of it.

I doubt that most users of “simular” — with a “u” in the middle — know its true meaning.

Solution:
Use the adjective “simular” when referring to something that is false or simulated or counterfeit. Use the adjective “similar” when referring to a likeness or resemblance.