f, letter that corresponds to the sixth letter of the Greek, Etruscan, and Latin alphabets, known to the Greeks as digamma.

The sound represented by the letter in Greek was a labial semivowel similar to the English w. This sound had disappeared early from the Ionic and Attic Greek dialects, so that the Ionic alphabet, which eventually came into general use in Greece, contained no digamma. It was retained, however, for some time in many local dialects and alphabets, including that from which the Etruscan (and through it the Latin alphabet) was derived.

None of the various Greek forms occur in the Semitic alphabets. Its origin in the Greek alphabet has been a matter of dispute, some maintaining that it descends from Semitic vau and others, less convincingly, maintaining that it was merely differentiated from the preceding letter E by the omission of a horizontal stroke. In either case it is probable that the Greeks were not the innovators, since a form of the letter occurs in the Lydian alphabet. The letter was probably contained in an Asian alphabet from which the Greek, Lydian, and Etruscan were derived.

In some very early Latin inscriptions, f was used in combination with h to represent the unvoiced labial spirant (English f). The h was soon dropped, and the sound was represented by the letter f alone. It was not required in Latin to represent the bilabial semivowel (w), for the Latins had taken the letter V to represent both this sound and the corresponding vowel (u). The letter f has represented the unvoiced labial spirant ever since.

In the Faliscan alphabet the letter had the curious form resembling an arrow pointing up. The Latin cursive of the 5th century ce employed a lengthened form, and the letter was generally extended below the line in uncial writing. In Irish writing of the 7th century the form came to resemble the modern f, and the Carolingian added further rounding of the top. From this developed the modern minuscule f.