An Etymological Dictionary of Astronomy and Astrophysics

1. To have the same views, emotions, etc.; harmonize in opinion or feeling (often followed by with).
   

2. To give consent; assent (often followed by to).
   

3. To come to one opinion or mind; come to an arrangement or understanding; arrive at a settlement.
   

4. To be consistent; harmonize (usually followed by with).
   

5. To correspond; conform; resemble (Dictionary.com).

Etymology (EN): M.E. agre, agreen, from O.Fr. agreer “to receive with favor, take pleasure in,” from phrase a gré “favorably, of good will,” from L. → ad- “to” + gratum “pleasing,” neuter of gratus
“pleasing, agreeable,” from PIE root *g^wer- “to praise;” cf. Pers. gerâmi “dear, revered,” from Av. gar- “to praise;” Skt. grnati “sings, praises,” Lith. giriu “to praise, celebrate.”

Etymology (PE): Infinitive from sâcan, → agreement.