From kathab; a thing written, the characters, or a document (letter, copy, edict, poem) -- writing.
see HEBREW kathab
H4385. miktab
מִכְתָּב noun masculine2 Chronicles 21:12 writing; — absolute ׳מ Deuteronomy 10:4 + 5t.; construct מִכְתַּב Exodus 32:16 2t.; —
1 = handwriting הוּא אֱלֹהִים מִכְתַּב וְהַמִּכְתָּב Exodus 32:16.
2 = thing written, Exodus 39:30 (accusative of congnate meaning with verb with כָּתַב), Deuteronomy 10:4; specifically a royal enactment or edict (= כתם כְּתָב 4), 2 Chronicles 35:4 "" כְּתָב, 36:22 = Ezra 1:1; a prophetic writing 2 Chronicles 21:12.
3 in a title, ׳מ לְחִזְקִיָּהוּ Isaiah 38:9 Writing of Hezekiah.