1: ποίμνη
(Strong's #4167 — Noun Feminine — poimne — poym'-nay )

akin to poimen, "a shepherd," denotes "a flock" (properly, of sheep), Matthew 26:31; Luke 2:8; 1—Corinthians 9:7; metaphorically, of Christ's followers, John 10:16 , RV, for the erroneous AV, "fold." What characterizes Christ's sheep is listening to His voice, and the "flock" must be one as He is one.

2: ποίμνιον
(Strong's #4168 — Noun Neuter — poimnion — poym'-nee-on )

possibly a diminutive of No. 1, is used in the NT only metaphorically, of a group of Christ's disciples, Luke 12:32; of local churches cared for by elders, Acts 20:28,29; 1—Peter 5:2,3 .