in vs at

Please have a look at the sentences below

  1. He’s good at grammar
  2. He’s bad at grammar
  3. He’s weak in grammar
  4. He’s strong in grammar
  5. He’s poor in grammar (is this ok?)

Why is it at for some adjectives and in for others?


Good question! There are of course fixed idiomatic uses, which as you know can’t be explained logically but I’ll try to suggest differences for good/bad/weak/strong/poor in or at. Broadly I would say that ‘in’ is more specific and ‘at’ is more general. If you say: ‘he’s good at grammar’, you are talking generally about grammar without talking about any particular aspects of grammar. If you say: he’s good in a crisis/an emergency/difficult situations, you are being more specific as you are talking about his ‘good’ behaviour/ability in those circumstances. The other use for ‘in’ with strong etc would be if you were referring to a particular ability or lack of it in a school/academic sense. The teacher could say: Charlie is good/poor in French where the suggestion is that Charlie is like that in his French class/exams at school.

Hope this throws some light.