1.to assent, approve, or agree fully, Aesch., etc.
2.c. acc. rei, to concede, agree to, grant, Plat., Xen.; absol., ξύμφημί σοι I grant you, Plat.; ξύμφαθι ἢ ἄπειπε say yes or no, id=Plat.
3.c. acc. et inf. to agree that . . , Soph., Plat.
4.c. inf. fut. to promise, Xen.