1 difficult

2 challenging

3 straitened circumstances

4 difficult situation

1 difficult (to...)

2 problem

3 difficulty

4 difficult

5 not good

1 hard to (predict, imagine etc)

1 to feel unwell

2 to suffer pain

3 to be difficult to bear

1 seldom

2 rare

3 hard to come by

1 lit. An interval of time is worth an ounce of gold, money cannot buy you time. (idiom)

2 fig. Time is precious and must be treasured.

1 a snap of the fingers (idiom); in a flash

2 in the twinkling of an eye

1 lit. a single post cannot prop up a falling house (idiom)

2 fig. one is helpless alone

1 lit. once said, a team of horses cannot unsay it (idiom); a promise must be kept

1 hard to explain in a few words (idiom); complicated and not easy to express succinctly