अगर वह झूठ बोलेगा, तो माँ बहुत उदास होगी।

It is the Hindi if ... then pattern.

• अगर = if
• तो = then

So अगर वह झूठ बोलेगा, तो माँ बहुत उदास होगी। is structured literally like:

• If he lies,
• then mother will be very sad.

A useful point: तो is often optional in Hindi, but it is very common because it makes the result clause clearer.

That is a very common question, and the short answer is: Hindi and English do not handle future conditions the same way.

In Hindi, for a real future possibility, it is very normal to use the future in both clauses:

• अगर वह आएगा, तो मैं जाऊँगा।
• अगर वह झूठ बोलेगा, तो माँ बहुत उदास होगी।

In English, we normally say:

• If he comes, I will go.
• If he lies, mother will be very sad.

So even though English avoids will after if, Hindi does not have that same restriction.

Yes, sometimes.

You may also hear:

• अगर वह झूठ बोले, तो माँ बहुत उदास होगी।

This is also grammatical. Very roughly:

• बोलेगा sounds natural for a more concrete future situation.
• बोले can sound a bit more neutral, formal, or less tied to a definite future event.

For a learner, the important thing is that बोलेगा in this sentence is perfectly normal.

वह can mean all of those, depending on context.

It can mean:

• he
• she
• that

In this sentence, the verb बोलेगा is masculine singular, so the most likely meaning is he. If the subject were clearly female, you would usually expect:

• अगर वह झूठ बोलेगी, तो माँ बहुत उदास होगी।

So वह itself does not show gender, but the verb often does.

Yes. झूठ बोलना is the standard Hindi expression for to lie.

Breakdown:

• झूठ = lie / falsehood
• बोलना = to speak / to say

Together:

• झूठ बोलना = to tell a lie / to lie

So वह झूठ बोलेगा literally looks like he will speak a lie, but idiomatically it simply means he will lie.

Because माँ is feminine singular, and the verb होना in the future agrees with it.

• माँ ... होगी = mother ... will be
• पिता ... होंगे / होगा would be different depending on number and formality

So here:

• माँ बहुत उदास होगी = mother will be very sad

Also note that उदास does not change form here. The agreement is shown by होगी.

You can leave it out.

Both are possible:

• अगर वह झूठ बोलेगा, तो माँ बहुत उदास होगी।
• अगर वह झूठ बोलेगा, माँ बहुत उदास होगी।

With तो, the sentence sounds a bit more clearly divided into condition and result. In everyday Hindi, using तो after अगर is very common.

Hindi normally puts the verb at the end of the clause, so both parts end with verbs:

• वह झूठ बोलेगा
• माँ बहुत उदास होगी

That is a very typical Hindi pattern.

Also:

• बहुत comes before the adjective उदास
• the if clause often comes first
• the result clause comes after it

So the sentence order is very natural and standard.

बहुत means very here.

So:

• उदास = sad
• बहुत उदास = very sad

It is functioning as an adverb modifying the adjective उदास.

The mark ँ shows nasalization.

So माँ is pronounced roughly like maa with a nasalized vowel. This is the standard spelling for mother / mom.

For learners, the main thing to remember is:

• माँ = mother, mom

and the nasal sign is part of the normal written form.

Good question. In standard written Hindi, वह is the usual form. In everyday speech, people very often say वो.

So:

• वह = more formal/standard written form
• वो = very common spoken form

This sentence uses the standard written style:

• अगर वह झूठ बोलेगा...

But in conversation, many speakers would naturally say:

• अगर वो झूठ बोलेगा...