Equal Comparisons: "as... as"

The comparison structure as... as is used in English to show that two things are equal in a particular quality (adjective) or manner (adverb). For example, saying someone is as tall as their brother means they share the same height. When negated, not as... as indicates that the second item has more of the quality than the first.

To form a positive comparison, place the base adjective or adverb between two "as" particles: as + adjective/adverb + as (e.g., as fast as a bullet). In negative comparisons, place "not" before the first "as" (not as + adjective/adverb + as), or optionally use not so... as in more formal style (e.g., not so expensive as the other one).

A common learner mistake is using comparative adjectives inside this structure (e.g., saying as taller as instead of as tall as). Another frequent error is using a different particle instead of the second as, such as than or like under the influence of other comparative structures (e.g., writing He is as fast than me instead of He is as fast as me). Remember to use subjective pronouns (e.g., as tall as I [am]) in formal contexts, though objective pronouns (as tall as me) are common in casual speech.