predicate and subject in the copular clause

The predicate (faisnéis) of a sentence is the "sentence statement ".
In a "normal" sentence this would be formed by the verb (predicative verb).

There are also sentences in which the verb is not the sole predicate of the sentence, but simply the introduction (so-called. non-predicative verbs).
Even the German verb "sein" is in this sense a non-predicative verb.
The actual statement occurs then in an identification ("He is Paul") or classification ("He is a donkey "). The predicate is then formed by a noun (predicate noun: "Paul", "donkey").
Also an adjective (predicative adjective) may form the predicate ("He is big ")

In the sentence "He is a student", "a student" is the predicate, "is" only couples it with the subject ("he") The "sentence statement " is here that he is a student.
The sentence: "he is big" says something about the quality of size. (hence big = predicate)
In the sentence: "he reads" is the action of reading the sentence statement (so reads = predicate).
If a noun is the predicate ("predicate noun ") this is often falsely termed as "object". As opposed to an object, it is always in the nominative and not in the accusative.

In Irish, the copula comes in place of the verb "to be " in sentences such as "he is a student", in part also in sentences like "he is big".

In identificatory clauses ("the man is the student") it is often difficult to discern subject from predicate, as both could be swtiched without a change in meaning (man = student)

In German and in English, one has the syntax "SPO" (subject - predicate - object)
This is why the subject comes first ("the man"), the predicate ("the student") follows.
If a pronoun occurs, this is always the subject ("he is the student", "Are you Paul?").
If one wishes to shift the emphasis to the pronoun, one only can do so with the aid of vocal or italic stress (Are you Paul?), it remains the subject (Are you Paul? / Are you Paul?)
So, in German or English, neither the word order nor the grammatical predicate definitive, only the stress says something about the desired logical sentence statement (the man is the student / the man is the student)!

In Irish, the emphatic part is always the grammatical and logical predicate and is then shifted in the necessary position!
In other words, if one wants to emphasize something in such sentences, one moves it into the predicate position!

In Irish, the order "PSO" is the rule (predicate - subject - object)
For copular clauses, then: copula - predicate - subject.
So:
Is é an dalta an fear = the man is the student. (predicate: an dalta = the student)
Is é an fear an dalta = the man is the student / the student is the man (predicate: an fear = the man)

deviations from the PSO-rule in the copular clause

In identificatory clauses, in some cases, (personal pronouns of the 1st and 2nd person) the syntax is switched and PSO no longer applies.
i.e. the pronoun of the 1st and 2nd person (mé, tú, sinn, muid, sibh) occurs always directly after the copula, no matter if it's the predicate or the subject.

The cause of this could be the substitution of older conjugated forms of the copula (e.g. "am" = I am) through the modern copular form + pronoun ("is mé" = I am), which simply takes the place of "am" in the sentence:
"Is mé an fear" = I am the man (Altirisch approx: "Am in fer")

The (always unstressed) "mé" is here the subject, despite its position.
A sentence like: "*Is é an fear mé" (as would be expected according to the PSO-rule) would be wrong.
In order to avoid such confusion, the personal pronoun is then made to be the predicate of the sentence. Then, the PSO-rule applies again.
Since the predicate is always the emphasized part of the sentence (see above), one uses other ("emphatic") forms of the pronouns:
"Is mise an fear = I am the man (actual translation: the man is me)
The fact that the pronoun is ther predicate here can only be seen due to the emphatic form, while unstressed (normal) forms of the pronoun show that it is the subject.

(One could also simplify this to say that a pronoun of the 1st and 2nd person is always the predicate. Although, the lack of stress of "mé" and "tú" would be disturbing.)

For personal names a similar rule applies: they too stand as the subject before the actual predicate. But they are still separated from the copula by a subpredicate (é/í/iad), so that, at least formally, the PSO-rule applies.
e.g.: Is é Pól an múinteoir = Paul (subject) is the teacher (predicate).

For those who find these complicated rules to be too much, should orient themselves by using examples:
Is mise an múinteoir = I am the teacher
Is tusa an múinteoir = You are the teacher
Is eisean an múinteoir = He is the teacher
Is é an múinteoir é = He is the teacher
Is é an múinteoir an fear = The man is the teacher
Is é an fear an múinteoir = The man is the teacher
Is é Pól an múinteoir = Paul is the teacher