-gram repr. Gr. grámma something written, letter of the alphabet, rel. to gráphein write in (i) words directly derived from Gr., as anagram, diagram, program(me), or modelled on Gr. types, as chronogram, logogram, (ii) words compounded with a numeral with grámma (or grammḗ line), as monogram, pentagram.
Also, in the denominations of weight in the metric system, repr. GRAMME.

-gram¹ • comb. form in nouns denoting something written or recorded (esp. in a certain way): cryptogram heliogram. -gram² • comb. form in nouns denoting a novelty greeting or message as a humorous or embarrassing surprise for the recipient: kissogram.

-gram combining form denoting a record; tracing.