Yes, annex is playable
...and is worth 14 points.
Found in the following dictionaries
Enable (Words with friends)
SOWPODS (Collins Scrabble Words)
OTCWL2014 (NASPA Word List 2014)
TWL06 (NASPA List 2006)
"Annex" Definition
noun
A building added on to a larger one or an auxiliary building situated near a main one.
An addition, such as an appendix, that is made to a record or other document.
something as an expansion or supplement as.
An added stipulation or statement .
A subsidiary or supplementary building or structure .
verb-transitive
To add or attach, as an attribute, condition, or consequence.
To append or attach, especially to a larger or more significant thing.
To incorporate (territory) into an existing political unit such as a country, state, county, or city.
verb
To attach as a quality, consequence, or condition.
To join together materially .
To add to something earlier, larger, or more important.
To incorporate (a country or other territory) within the domain of a state.
To obtain or take for oneself.
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