Be is one of the vital word in English. it has 2 functions to form sentences. As a structural meaning word, be need others to be used or 'to survive'. it means that be cannot stand alone.

For examples;

he is my uncle.

In the senence above, be /is/ becomes a Bridge to combine or to connect between the personal pronoun.subject /he/ and the complement /my uncle/. Some says that be is a 'Linking-Verb'.

There are 8 kinds of be(s) in English, they are;

/is/, /am/, /are/, /was/, /were/, /be/, /been/, /being/

All the be(s) are concentrated or devided into 4 positions. Look at this following illustrations!

As a be-present(is,am,are), it determines the use of be in simple present tense specially to build a nominal sentence and present continuous tense. As a be-past(was,were), it helps to build a simple past and past continuous tense. As a be-future, it is used to build a simple/present future tense and present future continuous tense. As a be-participle, it assists to build a perfect tense, either in nominal or verbal sentence. And be 'being' is commonly used to build a free adjunct expression and continuous tense in passive voice.

So, what is the use of BE ? Read more ...... .

There are two functions of be in English, they are:

1. As a verb
2. As an auxilliary

As a verb

/be/ builds a nominal sentence. the position and the existance of be in this form is the same as lexical-verb (present verb, past verb, participle verb and the ing form verb), that is, a vital word in a sentence. When the be is omitted in nominal sentence, the existance of a sentence is nothing.

For examples:

I  am late.
you are late. (either you as a singular personal pronoun or plural personal pronoun)
we are late.
they are late.
he is late.
she is late.
it is late.

it is impossible for us to say : " I late" instead of "I am late"

So, the be /am/ is positioned as a bridge. without the bridge, cars or people can not accross the river or sea. Some say that be is also called "Linking-verb".

As an auxilliary

Auxilliary is similar to a helper. it means that the existance and the use of be is to help to form continuous tense form. because of this, be is commonly used in verbal sentence.
So, what does the be do for it?

For examples:

Present continuous tense
past continuous tense
present perfect continuous tense
present future tense, etc

In the other words, be, as an auxilliary will be found in continuous or progressive tenses.