A phonogram is a grapheme (written character) which represents a phoneme

Phoneme

In a language or dialect, a phoneme is the smallest segmental unit of sound employed to form meaningful contrasts between utterances....

 (speech sound) or combination of phonemes, such as the letters of the Latin alphabet

Latin alphabet

The Latin alphabet, also called the Roman alphabet, is the most recognized alphabet used in the world today. It evolved from a western variety of the Greek alphabet called the Cumaean alphabet, which was adopted and modified by the Etruscans who ruled early Rome...

 or the Japanese kana

Kana

Kana are the syllabic Japanese scripts, as opposed to the logographic Chinese characters known in Japan as kanji and the Roman alphabet known as rōmaji...

. For example, "igh" is an English-language phonogram that represents the hard "I" sound in "high." Whereas the word phonics refers to the sounds, the word phonogram refers to the letter(s) that represent that sound.

This contrasts with logogram

Logogram

A logogram, or logograph, is a grapheme which represents a word or a morpheme . This stands in contrast to phonograms, which represent phonemes or combinations of phonemes, and determinatives, which mark semantic categories.Logograms are often commonly known also as "ideograms"...

s, which represents words and morpheme

Morpheme

In linguistics, a morpheme is the smallest semantically meaningful unit in a language. The field of study dedicated to morphemes is called morphology. A morpheme is not identical to a word, and the principal difference between the two is that a morpheme may or may not stand alone, whereas a word,...

s (meaningful units of language), and determinative

Determinative

A determinative, also known as a taxogram or semagram, is an ideogram used to mark semantic categories of words in logographic scripts which helps to disambiguate interpretation. They have no direct counterpart in spoken language, though they may derive historically from glyphs for real words, and...

s, silent characters used to mark semantic categories

Semantics

Semantics is the study of meaning. It focuses on the relation between signifiers, such as words, phrases, signs and symbols, and what they stand for, their denotata....

. They are letters.