Apart means separated by a distance, or into pieces. Stand apart, take it apart, worlds apart.
It does two jobs: distance between things, and separation into parts. Apart from means except for in British use and in addition to in some others, which occasionally causes real ambiguity. Worlds apart and poles apart are fixed phrases for total difference. Note that the word comes from a Latin phrase meaning to the side.
1adverbapartSeparated by a distance.
“Plant the tomato seedlings at least half a metre apart so they have room to grow.”
2adverbadverbInto pieces.
“The old chair fell apart when he sat on it.”
Too few real examples of this word to estimate which sense is commonest.
apart is a separation.
Anglo-Norman a part comes from Latin ad partem, to the side. Part, partition and portion come from the same part.
Latin
ad partem — to the side
Anglo-Norman
a part
Middle English
apart
English, today
apart
From Middle English apart, aparte, a-part, a part, from Anglo-Norman a part, from Latin ad partem (“to the side”).
Etymology from Wiktionary, CC BY-SA