Meaning of FIRM in English

FIRM

(CERTAIN) [adjective] -er, -est - certain or fixed in a belief, opinion, etc. and unlikely to change, or so certain as to be beyond doubt or questionHe is a firm believer in traditional family values.We're appealing to the government for a firm commitment to help these refugees.Some people still claim that there is no firm evidence linking smoking with lung cancer.They've expressed an interest in working with us, but we're still waiting for a firm proposal from them.I was always very firm with my children - they knew the rules and I made sure they kept to them.Firm in the belief that they could never be caught, they didn't bother to hide the clues which eventually betrayed them to the police.

Cambridge English vocab.      Кембриджский английский словарь.