proclitic

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A clitic that is attached to the beginning of another word.
• adjective Of or relating to a proclitic or proclisis; forming an accentual unit with the following word.

from The Century Dictionary.

• In Greek grammar, dependent in accent upon the following word: noting certain monosyllabic words so closely attached to the word following as to have no accent.
• noun In Greek grammar, a monosyllabic word which leans upon or is so closely attached to a following word as to have no independent accent.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Gr. Gram.) Leaning forward; -- said of certain monosyllabic words which are so closely attached to the following word as not to have a separate accent.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun linguistics A clitic which phonetically joins with the following word. In English, the dialectal form t' is an example. In Arabic, conjunctions and prepositions that have only one letter, such as و (wa-), always attach as a prefix to the following word.