一人で地下鉄に乗るのは危ないですか。

one; best; first; foremost; beginning; start; bottom string (on a shamisen, etc.)

-ian (e.g. Italian); -ite (e.g. Tokyoite); indicates nationality, race, origin, etc.; -er (e.g. performer, etc.); person working with ...; indicates expertise (in a certain field); (usu. in compound words) man; person; people

indicates location of action; at; in; indicates time of action; indicates means of action; cause of effect; by; and then; so; indicates continuing action; indicates certainty, emphasis, etc.

underground train; subway

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

to get on (train, plane, bus, ship, etc.); to get in; to board; to take; to embark; to get on (e.g. a footstool); to step on; to jump on; to sit on; to mount; to reach; to go over; to pass; to follow; to stay (on track); to go with (the times, etc.); to take part; to participate; to join; to get into the swing (and sing, dance, etc.); to be deceived; to be taken in; to be carried; to be spread; to be scattered; to stick; to attach; to take; to go on

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

dangerous; risky; hazardous; perilous; precarious; in danger; in jeopardy; critical; grave; at risk; uncertain; unreliable; insecure; unsteady; doubtful; close (i.e. a close call); narrow; look out!; watch out!

be; is

indicates a question (sometimes rhetorical); or; whether or not; some- (e.g. something, someone); indicates doubt, uncertainty, etc.; emphatic prefix; suffix forming adjectives or adverbs; in that way