Greek: τελειος [teleios] (Adjective). From τελος [telos]. Finished, complete, "the one that has reached the goal". Perfect.

τελειος [teleios] appears 19 times in the NT:

(1, 2) Matthew 5: 48
Be ye therefore perfect¹, even as your Father which is in heaven is perfect². - ¹τελειοι [teleioi] Nom. pl. masc. / ²τελειος [teleios] Nom. sing. masc.

(3) Matthew 19: 21
Jesus said unto him, If thou wilt be perfect, go [and] sell that thou hast, and give to the poor, and thou shalt have treasure in heaven: and come [and] follow me. - τελειος [teleios] Nom. sing. masc.

(4) Romans 12: 2
And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what [is] that good, and acceptable, and perfect, will of God. - τελειον [teleion] Nom. sing. neuter.

(5) 1 Corinthians 2: 6
Howbeit we speak wisdom among them that are perfect: yet not the wisdom of this world, nor of the princes of this world, that come to nought: - τοις τελειοις [tois teleiois] Dat. pl. masc. ("among them that are perfect" - εν τοις τελειοις [en tois teleiois] Lit: "in the ones that have reached the goal").

(6) 1 Corinthians 13: 10
But when that which is perfect is come, then that which is in part shall be done away. - το τελειον [to teleion] Nom. sing. neuter.

(7) 1 Corinthians 14: 20
Brethren, be not children in understanding: howbeit in malice be ye children, but in understanding be men. - τελειοι [teleioi] Nom. pl. masc.

(8) Ephesians 4: 13
Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ: - τελειον [teleion] Accus. sing. masc. ("unto a perfect man" - εις ανδρα τελειον [eis andra teleion]).

(9) Philippians 3: 15
Let us therefore, as many as be perfect, be thus minded: and if in any thing ye be otherwise minded, God shall reveal even this unto you. - τελειοι [teleioi] Nom. pl. masc.

(10) Colossians 1: 28
Whom we preach, warning every man, and teaching every man in all wisdom; that we may present every man perfect in Christ Jesus: - τελειον [teleion] Accus. sing. masc.

(11) Colossians 4: 12
Epaphras, who is [one] of you, a servant of Christ, saluteth you, always labouring fervently for you in prayers, that ye may stand perfect and complete in all the will of God. - τελειοι [teleioi] Nom. pl. masc.

(12) Hebrews 5: 14
But strong meat belongeth to them that are of full age, [even] those who by reason of use have their senses exercised to discern both good and evil. - τελειων [teleiôn] Gen. pl. masc.

(13) Hebrews 9: 11
But Christ being come an high priest of good things to come, by a greater and more perfect tabernacle, not made with hands, that is to say, not of this building; - τελειοτερας [teleioteras] Gen. sing. fem. Comparative.

(14, 15) James 1: 4
But let patience have [her] perfect¹ work, that ye may be perfect² and entire, wanting nothing. - ¹τελειον [teleion] Accus. sing. neuter. / ²τελειοι [teleioi] Nom. pl. masc.

(16) James 1: 17
Every good gift and every perfect gift is from above, and cometh down from the Father of lights, with whom is no variableness, neither shadow of turning. - τελειον [teleion] Nom. sing. neuter.

(17) James 1: 25
But whoso looketh into the perfect law of liberty, and continueth [therein], he being not a forgetful hearer, but a doer of the work, this man shall be blessed in his deed. - τελειον [teleion] Accus. sing. masc. ("into the perfect law" - εις νομον τελειον [eis nomos teleion] Lit: "in law perfect").

(18) James 3: 2
For in many things we offend all. If any man offend not in word, the same [is] a perfect man, [and] able also to bridle the whole body. - τελειος [teleios] Nom. sing. masc.

(19) 1 John 4: 18
There is no fear in love; but perfect love casteth out fear: because fear hath torment. He that feareth is not made perfect in love. - η τελεια [hê teleia] Nom. sing. fem.