bad (at), poor (at), weak (at), uncomfortable with / hard to get along with (of a person)

weak point

he / distal demonstrative, something far off removed from both speaker and listener: that / boyfriend

mathematics (field of study)

distal demonstrative, something far off removed from both speaker and listener: that, yon / particularly, male personal third person pronoun: he / by extension from he: boyfriend

he; boyfriend

applied mathematics

(mathematics) pure mathematics

mathematician

Alternative spelling of 組合せ数学 (“combinatorics”)