This is a good question because many ESL learners have a problem the expression "as ____ as". This expression is used to compare two or more things. .... as good (adjective) as .... .... as cold (adjective) as .... ... as difficult (adjective) as ... .... as quickly (adverb) as ... .... as slowly (adverb) as .... Many English learners use the expression "so (adjective or adverb) as" and it is wrong. When comparing one thing to other things we should always use the expression "as (adjective or adverb) as ...".