Through

Through is a word with multiple grammatical functions in English. Primarily a preposition and an adverb, it can indicate movement from one side to another, passage via a space, duration, or means by which something is accomplished. Its precise sense is determined by context and by the verbs and nouns it attaches to.

As a preposition, through introduces the path or channel of action: “walk through the park,” “drive through the tunnel,” “read through a document.” It can indicate that something goes from one side to the other within a space, or that something is accomplished by means of a process: “learned through practice” or “transmit through a relay.” It also occurs in expressions specifying duration: “through the night” or “throughout the year.”

As an adverb, through can indicate completion or progression: “the project went through” (informally meaning approved or completed) or “we worked through the night.” It is common in phrasal verbs such as go through, push through, or break through, which extend or alter the base meaning to emphasize passage, completion, or penetration.

An idiomatic use is through and through, meaning completely or thoroughly. Related forms such as throughout share the root but refer to distribution across an entire area or time. The word is from Old English thrūh, with cognates in other Germanic languages. Alternative spellings include thru in informal contexts; however, through remains the standard spelling in formal writing.