Incorrect spelling

excells

Incorrect spelling, explanation: excells is an incorrect form because unlike the correct one – excels – it seems like it underwent a completely different derivation process. Because as of now there is only one l in excel, excells seems like it was made out of the prefix ex- and cells (as in: plural form of cell), which would suggest a completely different meaning not at all related to the original.


Correct spelling

excels

Correct spelling, explanation: excels is a third-person singular present form of the verb excel (he/she/it excels). The word originates from Latin excellere, but the word lost the double l over time in order to suit the English standards better.

Definition of excels:
Verb, third person singular
1. to perform extremely well in something; to be very good at something
Not only is she very sweet, but she also excels in her studies.
Mark excelled at tennis, he even got qualified for an ATP tournament.