Enclitic

An enclitic word is one which does not normally have an accent but attaches to the previous word for the purposes of applying the accenting rules. Thus, depending on where the accent of the previous word is, the enclitic may or may not affect how the previous word is accented. In lexicons, enclitic words are presented with accents. There are also exceptional circumstances where enclitic words are accented in sentences.

The effect of an enclitic word on accenting is complex and need not preoccupy us if our only aim is to learn to read greek. It's just useful to know so that if we ever notice differences in the accenting of the same word we might have a clue why.

Example of enclitic effect

 * τὸ ὄνομά σου - from Matthew 6:9b, the first line of the Lord's Prayer. σου doesn't have an accent of its own but pushes its accent onto the previous word, or rather it attaches to the previous word for the purpose of applying accenting rules. Since accents can only be placed on the last three syllables of a word-group, the original accent of ὄνομα is too early. So another accent is added, ὄνομά.
 * Note that the enclitic effect does not cause the accent in the previous word's last syllable to drop to a grave. This is part and parcel of being treated as one word-group for accenting rules, so they are not two separate words in composition.

Exceptions

 * ἐστίν or εἰσίν are used to signify the existence of something. In English translation, this is recognisable as those times when ἐστίν or εἰσίν are translated "it is". E.g. οὕτως γὰρ πρέπον ἐστὶν ἡμῖν πληρῶσαι πᾶσαν... (Matthew 3:15).
 * When ἐστίν or εἰσίν are at the head of a sentence or clause.
 * When an enclitic is preceded by the unaccented word οὐ, οὐκ, οὐχ. Makes sense, otherwise the sentence will go on for too long without an accent!