In Japanese and Turkish, one way to distinguish them is like this. 

He is a doctor. 

Kare-ha isha-desu. 

O, doktordur. 

He is (a) doctor.

He is the doctor:

 Isha-ha kare-desu. 

Doktor, odur. 

(The) doctor is him.

On 2017(09M7W03)246, at 13H39M40S, Raymond Brown <[log in to unmask]> wrote:

On 02/09/2017 19:38, J S Jones wrote:
> On Sat, 2 Sep 2017 10:26:10 -0600, Logan Kearsley wrote:
>> English typically relies on definiteness in a predicate nominal:
>> "He is a doctor." (Proper Inclusion- he is a member of the
>> category of "doctors".)
>> "He is the doctor." (Equation- he and the doctor are the same person.)
>> So, do you worry about distinguishing those cases, and if so, how do you do it?