An allegory (Greek -agoria, speaking, so literally ‘speaking otherwise’) is a story, poem, or picture in which there is another, hidden meaning; an allergy (Greek ergon, work, so something working differently) is a damaging immune response by the body to a substance.
Allotropes are the different physical forms in which an element can exist, such as carbon, which can occur as graphite or as diamond; allopathy is the treatment of disease with drugs having effects opposed to the symptoms (contrasted with homeopathy).
In linguistics, allographs are alternative forms of a letter of an alphabet, for example its capital, lower case, and italic forms; allophones are the various ways sounds can be pronounced, which do not contribute to distinctions of meaning.