Features use of a personal form of the verb "БЫТЬ" (TO BE)

The Russian language has features use of a personal form of the verb «БЫТЬ» [být′]- TO BE.
These features are related to the present tense.
However, let’s have a look at this verb at all tense examples.

Present Tense.

Zero form «ЕСТЬ» [yést′] – AM, IS, ARE
! It is not used in speech, and replaced by a dash (-) in writing:

Я - врач. [Ya - vrach]	I am a doctor.
Он/она - инженер. [On/aná - inzhinér]	He/she is an engineer.
Тигр - хищник. [Tigr - khíshch′nik]	The tiger is a predator.
Ты/вы - учитель. [Ty/vy - uchítil′]	You are a teacher.
Мы/они - спортсмены. [My/aní - spartsmény]	We/they are sportsmen.

Past Tense.

Я был(а) врачом. [Ya byl(á) vrachóm]	I was a doctor.
Он/она был(а) инженером. [On/aná byl(á) inzhinéram]	He/she was an engineer.
Небо было пасмурным. [Néba býla pásmurnym]	The sky was cloudy.
Ты/вы был(а)/были учителем. [Ty/vy byl(á)/býli uchítilim]	You were a teacher.
Мы/они были спортсменами. [My/aní býli spartsménami]	We/they were athletes.

Future Tense.

Я буду врачом. [Ya búdu vrachóm]	I will be a doctor.
Он/она будет инженером. [On/aná búdit inzhinéram]	He/she will be an engineer.
Небо будет пасмурным. [Néba búdit pásmurnym]	The sky will be cloudy.
Ты/вы будешь/будете учителем. [Ty/vy búdish′/búditi uchítilim]	You will be a teacher.
Мы/они будем/будут спортсменами. [My/aní búdim/búdut spartsménami]	We/they will be athletes.