insufficient

Từ điển Oxford Advanced Learner 8th

in·suf·fi·cient AW BrE [ˌɪnsəˈfɪʃnt] NAmE [ˌɪnsəˈfɪʃnt] adjective ~ (to do sth) | ~ (for sth) (formal)
not large, strong or important enough for a particular purpose
Syn: ↑inadequate
•insufficient time
•His salary is insufficient to meet his needs.
Opp: ↑sufficient
•The management paid insufficient attention to working conditions.
•There are fears that the existing flood barrier may prove insufficient.
Derived Words: ↑insufficiency ▪ ↑insufficiently

Word Origin:
late Middle English (in the sense ‘incapable, incompetent’): via Old French from late Latin insufficient- ‘not sufficing’, from in- ‘not’ + Latin sufficere ‘put under, meet the need of’ (from sub- ‘under’ + facere ‘make’).

Example Bank:
•I'm afraid we have insufficient evidence.
•There are fears that the existing flood barrier may prove to be insufficient.