そのパズルを解くのは難しかった。

that (something or someone distant from the speaker, close to the listener; actions of the listener, or ideas expressed or understood by the listener); the; um...; er...; uh...

puzzle

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to untie; to unfasten; to unwrap; to undo; to unbind; to unpack; to unsew; to unstitch; to solve; to work out; to answer; to dispel (misunderstanding, etc.); to clear up; to remove (suspicion); to appease; to dissolve (a contract); to cancel; to remove (a prohibition); to lift (a ban); to raise (a siege); to release (from duty); to relieve; to dismiss; to comb (out); to card; to untangle (hair)

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

difficult; hard; troublesome; complicated; serious (disease, problem, etc.); fussy; particular; fastidious; hard to please; displeased; gloomy; glum; sullen; serious (look); dirty; unclean; filthy; detestable; unpleasant; uncomfortable; creepy; spooky