late Middle English (denoting a deputy or delegate): from Latin substitutus 'put in place of', past participle of substituere, based on statuere 'set up'
Traditionally, the verb substitute is followed by for and means ‘put someone or something in place of another’, as in she substituted the fake vase for the real one. From the late 17th century substitute has also been used to mean ‘replace someone or something with something else’, as in she substituted the real vase with the fake one. This can be confusing, since the two sentences shown above mean the same thing, yet the object of the verb and the object of the preposition have swapped positions. Despite the potential confusion, the second, newer use is well established, especially in some scientific contexts and in sport (the top scorer was substituted with almost half an hour still to play), and is now generally regarded as part of normal standard English.