Meaning of “concentration” - Learner’s Dictionary

concentration

noun uk us /ˌkɒnsənˈtreɪʃən/
THINKING CAREFULLY [ U ]

B2 the ability to think carefully about something you are doing and nothing else

LARGE AMOUNT [ C, U ]

a large number or amount of something in the same place:

high concentrations of minerals

(Definition of “concentration” from the Cambridge Learner’s Dictionary © Cambridge University Press)