Answer:
the word similar means when to things are alike, it compares to congruent because congruent means thing are in harmony.
Things I would say are similar is a blanket and a sheet because they both provide coverage and warmth.
If I said things are similar it is because they are alike in meanings, or appearence.
I would use similar over congruent because congruent isn't a word you hear often. When you do hear it is mostly used to talk about angles and lines.