A possible alternative to "learning" is "lesson". The problem with "lesson" is that it can have two meanings: (a) a formal lecture given by a qualified person

A possible alternative to "learning" is "lesson". The problem with "lesson" is that it can have two meanings: (a) a formal lecture given by a qualified person to a class; (b) a fact that you learned from any person or even just a situation you were in. "Lesson" in the sense (b) is a direct substitute for "a learning", but I have to admit a few people might sometimes interpret it as (a) and be confused. But it depends on the context - if a project report has a "lessons learnt" heading I don't think any reader is going to expect that means meaning (a).