1) of one mind, of one accord
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 This word is made up of two words "sun" (together with) and psuchos
 (soul, self, inner life, or the seat of the feelings, desires,
 affections).  So the word refers to being united in spirit or
 harmonious (A&G).  Paul desired the Philippians to be united in
 their affections - one in Christ in all desires!  Used only here
 in the NT. (Wayne Steury)