Αυτό is for one horse (it is a horse=Αυτό είναι ένα άλογο) and αυτά for many horses (they are horses=Αυτά είναι άλογα)
Just as in English you would say "It is a horse" rather than "He is a horse".
αυτοί is masculine plural but άλογα is neuter plural, so the neuter plural αυτά is appropriate.
How do you say: It is a gentleman horse? It's a male.
Αυτός or αυτό ?
You'd still say αυτό. You could be more precise by using the adjective "male" in it's neuter grammar form. "Αυτό είναι ένα αρσενικό άλογο." = "This is a male horse."
Don't be confused...the word "male" "αρσενικός" is an adjective, and though it means male, it still has 3 grammatical genres, depending on the noun it defines. m:αρσενικός,, f:αρσενική/αρσενικιά, n:αρσενικό. eg: Ένας αρσενικός σκύλος A male dog Μία αρσενική αρκούδα A male bear Ένα αρσενικό περιστέρι A male pigeon
For male horses there is also the word "επιβήτορας", which means "stallion". But I guess it's used only as often and in the same context as the engilsh word.
So I suppose it could be used to differentiate between a male and female doctor? ενας καλη ιατρός
Exactly, because there is no different female word for ιατρός. So we say Μία καλή γιατρός , Ένας καλός γιατρός. or Μία καλή δικηγόρος, Ένας καλός δικηγόρος (a good lawyer).
Keep in mind there are many nouns that do have a separate female form and in that case we must change the gender of the noun too eg, teacher: Μια καλή δασκάλα, Ένας καλός δάσκαλος athlete: Μια καλή αθλήτρια, Ένας καλός αθλητής
So is the vocative for a lady doctor ιατρέ?
καλή μέρα, ιατρέ Μαρία.
Yes, the vocative for the word γιατρός is γιατρέ for both sexes. The spelling γιατρός is more common than ιατρός, which sounds a bit ancient and is mostly used for the creation of composite words (παιδίατρος, οδοντίατρος etc.)
μια καλή γιατρός with feminine article (γιατρός can be either masculine or feminine grammatically).
I got ιατρός from Cyprus. Is that perhaps why it sounds a bit ancient?
Because they are neuter plural :)
αυτοί would be masculine plural, αυτές would be feminine.
You would similarly not say Αυτοί είναι γυναίκες -- just as you would not say "he is a woman" or "she is a horse" in English.
Edit: I just saw that I answered essentially this question 3 months ago, right above your comment. Was the previous answer unsatisfactory?