Criterias.

You wrote it. Then deleted it. Then wrote “criteria.” Then weren’t sure that was right either.

English has a small group of irregular plurals – words that don’t follow the normal rules. They come from Latin and Greek, and they catch almost everyone out.

Including native speakers.

Criterion → criteria.
Thesis → theses.
Alumnus → alumni.

You don’t need to know the full list. You need to know the ones that appear in your professional world – and trust that getting the rest slightly wrong won’t stop anyone from understanding you.

Quick win: If you’re unsure of a plural, restructure the sentence. “The main criterion” sidesteps the problem entirely. One small change. Zero doubt.

💬 Which irregular plural catches you out most often?

— Christine