when, where

See is when. The objection to is when and is where may or may not be based on grammatical grounds, but unquestionably both phrases are childish, immature, and overused. A further objection is that when and where are often used in situations where their meanings are not applicable. For example, when has a meaning of time and is illogical in a sentence such as "This plan is when they refuse to let anyone under sixteen enter the theater."