I am a singer at my church. Oftentimes I have to choose a song written for a male’s vocal range, which means I have to sing the song in a male key but with my soprano voice. What is the official term for this? Am I singing the melody an octave above the male melody of the song? I only play music by ear and am terrible at reading music, so I don’t play an instrument for church, which makes it difficult to choose a song key. I’m trying to learn correct terms so I can communicate with the other vocalists correctly.
Am I singing the melody an octave above the male melody of the song?
Based on your description, most likely yes.
This is called transposition, you transpose the melody an octave up. In common language this would mean singing "the same notes but higher". If you transpose by an octave you can sing along the same recording, or the same accompaniment.
Transposing by an octave is simple, but sometimes it may not fit the song well in the vocal ranges of the performers. In such case the ensamble may choose to transpose by a different interval than octave. If the song is sung along a backing track, this requires a new backing track in the transposed key. If it's sung with instrumentalists, they need to play the accompaniment in a different key. For some instrumentalists transposing on the spot might be challenging, possibly they may need the music re-arranged in a different key by someone more skilled in music theory.
This is completely normal. Women's voices are in general an octave higher than men's voices, though of course a particular woman might have a voice slightly more or less than an octave higher than a particular man.
In the 19th century, entire song collections were published in different keys for high, medium, or low voice. Roughly speaking, sopranos and tenors would use the high version, mezzo sopranos and baritones would use the medium version, and altos and basses would use the low version. If a song was intended for a woman, a man could sing it an octave lower. If a song was intended for a man, a woman could sing it an octave higher. Many songs were not necessarily intended for one or the other, of course.
There are other possibilities, though. In modern popular styles, especially styles where the use of a microphone is common, it's not that unusual for a man with a high voice and a woman with a low voice to sing in the same octave. I'm thinking in particular of classic rock and roll of the 1950s and '60s -- you wouldn't likely want to sing a Chuck Berry song like Johnny B. Goode an octave higher.
As to the official term, well there really isn't one, other than "singing an octave higher." For the most part, it's not something that even needs to be discussed. If you hand some sheet music to a pianist, a guitarist, or even a whole band, and you hand the same sheet music to a man or a woman, nobody's normally going to say a word about what octave the singer is singing in. The band will play and the singer will sing.
This is made possible in part by the convention that song melodies are virtually always written in treble clef, and that men sing music written in treble clef an octave lower.
A given song might need to be transposed up or down somewhat less than an octave in order to adjust for the singer's high or low voice, but if you have some sheet music that you can sing comfortably in any octave without transposing it then just sing it in that octave and don't worry about it.
If the band is using or understands Nashville Number System they should be able to take any song and quickly transpose it. For example "Let it be" by the Beatles, "G D Em C" In Nashville number system that's 1 5 6m 4 in the key of G. If you were to take it down to D, The numbers are still 1 5 6m 4, but in the key of D that would be D A Bm G.
So if you've got a song -- and it's too high, you should be able to ask them to come down and they should understand what key its in. Many times I've seen singers go to the keyboardist and hum the first note in a key that is comfortable for the singer -- the keyboardist could then match the pitch and let the rest of the band know what key. Nashviller number system makes it easy for everyone to get in the right key. If they're not I've seen our keyboardist quickly write out the new parts for guitar and bass on the fly.