A — 1: πρεσβεύω
(Strong's #4243 — Verb — presbeuo — pres-byoo'-o )

denotes (a) "to be elder or eldest, prior in birth or age;" (b) "to be an ambassador," 2—Corinthians 5:20; Ephesians 6:20; for Philemon 1:9 see under AGED. There is a suggestion that to be an "ambassador" for Christ involves the experience suggested by the word "elder." Elder men were chosen as "ambassadors."

B — 1: πρεσβεία
(Strong's #4242 — Noun Feminine — presbeia — pres-bi'-ah )

primarily, "age, eldership, rank," hence, "an embassy or ambassage," is used in Luke 14:32; in 19:14, RV, "ambassage," for AV, "message."