Too is defined as also or in addition. It can also refer to something done to an excessive degree.(adverb)
See too in Webster's New World College Dictionary
Origin: stressed form of to, with differentiated sp.
See too in American Heritage Dictionary 4
Origin: Middle English to
Origin: , from Old English tō, to, furthermore; see de- in Indo-European roots. Usage Note: Some language critics have objected to the use of not too as an equivalent of not very, as in She was not too pleased with the results. In many contexts this construction is entirely idiomatic and should pass without notice: It wasn't too long ago that deregulation was being hailed as the savior of the savings and loan industry. It was not too bright of them to build in an area where rock slides occur. In these cases not too adds a note of ironic understatement. • Negation of too by can't may sometimes lead to ambiguities, as in You can't check your child's temperature too often, which may mean either that the temperature should be checked only occasionally or that it should be checked as frequently as possible. • Too meaning “in addition” or “also” is sometimes used to introduce a sentence: There has been a cutback in federal subsidies. Too, rates have been increasing. There is nothing grammatically wrong with this usage, but some critics consider it awkward.
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