KAKU firm, tight, hard, solid.

tashi(kameru) ascertain, confirm, verify.

kaku(taru), tashi(ka) sure, positive; accurate; reliable; sound, firm; clear, evident; genuine; able, competent; sober,sane; I think; if I remember right.

tashi(ka)ni certainly, doubtless.

tashi(ka)niwa for certain.

shika to certainly, definitely, exactly, firmly, fully.