puzzle _noun  

1-) a game or question that requires skill, knowledge, etc. to be solved

NOUNS

jigsaw 
・Some jigsaw puzzles have thousands of pieces.

word
・We did a type of word puzzle where the first letters of the answers form another word.

crossword 
・Dad was doing the crossword puzzle on the back page of his newspaper.

PUZZLE + NOUN
book
・She took a puzzle book on the train to pass the time.

VERBS

do
・I like doing crossword puzzles.

solve
・When you think you’ve solved the puzzle, you can check your answers at the back of the book.

2-) something that is difficult to understand or explain

ADJECTIVES

real
・It’s a real puzzle how these animals manage to survive the winter.

great
・His comments were a great puzzle to me.

scientific, biological, medical
・The question of how galaxies form is a scientific puzzle.

VERBS

solve
・I think I’ve solved the puzzle of what happened to the money.

piece together
・Detectives desperately tried to piece together the puzzle of his disappearance.

work out 
・Maybe together scientists can work out this puzzle.

pose, present
・How the disease is passed on poses a puzzle for scientists.

remain
・The true identity of this mystery woman remains a puzzle.

PREPOSITIONS

to
・I don’t know how he got the job – it’s always been a puzzle to me.

PHRASES

a piece of the puzzle 
・Police want to find this car, which they think is an important piece of the puzzle.

the solution to a puzzle
・A Cambridge scientist was the first to see the solution to this puzzle.

the key to the puzzle 
・Professor Jones thinks that he may have found the key to the puzzle.

sth is a bit of puzzle to sb
・Her sudden strange behaviour was a bit of a puzzle to her parents.