Translation guide
A Christian denomination known for door-to-door evangelism and use of the name Jehovah. In Japanese, the group is referred to by a direct translation of the English name.
Jehovah's Witnesses
Standard Japanese name for the religious group.
Referring to the organization or its members collectively.
This is the official and most common way to refer to Jehovah's Witnesses in Japanese. It is a direct translation of the English name.
Jehovah's Witnesses came to my house.
He is one of Jehovah's Witnesses.
Referring to an individual who is a Jehovah's Witness.
To specify an individual member, you can add の人 (person). This is natural when you want to emphasize the person rather than the group.
The person next door is a Jehovah's Witness.
Using 信者 (believer/follower) is also possible, but it can sound slightly more formal or religious-studies oriented.
In casual conversation, some people might shorten it to just エホバ (Ehoba), but this can be considered disrespectful. It's safer to use the full name.
That person seems to be a Jehovah's Witness.
She is a follower of Jehovah's Witnesses.