Unity or Union (John 10:30)

In the phrase "I and the Father are one" (ἐγὼ καὶ ὁ Πατὴρ ἕν ἐσμεν, John 10:30), the word ἕν is the neuter form of the Greek cardinal number for "one.” 

By using the neuter ἕν (hen) instead of the masculine εἷς (heis), the text implies a unity of essence, will, or action rather than a personal identity. If the masculine form had been used, it would suggest that the Father and the Son are the same person.

Jesus’s persistent claim in the Fourth Gospel is that he does the work of God, not his own work. He never says he is God. His point is that he is united with God.

Here is how the number "one" (nominative case) appears across the three grammatical genders:
• Masculine: εἷς (heis)
• Feminine: μία (mia)
• Neuter: ἕν (hen)

For Jesus’s identity and his work in the Fourth Gospel, see Yung Suk Kim, Truth, Testimony, and Transformation: A New Reading of the “I Am” Sayings of Jesus in the Fourth Gospel (Cascade, 2014).