gap ②break ③chink (in one's armor, armor) ④breach (of a relationship between people)

crevice ②spare moment ③chink (in one's armor, armor)

chink in the armor (armor)

draft ②cooling off of a relationship

closely

before one could

to watch for an unguarded moment

to seize an opportunity

one must constantly be on one's guard with ...

gap

niche market

God of the gaps

without any weak spot

to take advantage of one's carelessness

gap

vacant space

spare time ②small opening

crevice

caulking

void ratio

porosity

synaptic cleft

potential space

slit

time flies