知らない犬には気をつけなければならない。

to be aware of; to know; to be conscious of; to cognize; to cognise; to notice; to feel; to understand; to comprehend; to grasp; to remember; to be acquainted with (a procedure); to experience; to go through; to learn; to be acquainted with (a person); to get to know; to concern

dog (Canis (lupus) familiaris); snoop (i.e. a detective, a spy, etc.); loser; asshole; counterfeit; inferior; useless; wasteful

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

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

spirit; mind; heart; nature; disposition; motivation; intention; mood; feelings; atmosphere; essence

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 turn on; to switch on; to light up