Si el proyector no funciona, usaré la pizarra.

Because si without an accent means if.

Sí with an accent means yes.

So in this sentence, Si el proyector no funciona... means If the projector doesn’t work..., not Yes, the projector...

After si meaning if, Spanish normally uses the present tense for real or possible future situations.

So Spanish says:

Si el proyector no funciona, usaré la pizarra.

Literally, that is like: If the projector doesn’t work, I will use the board.

English often uses the present tense after if too, so this pattern is actually quite similar:

• If it rains, I’ll stay home.
• Si llueve, me quedaré en casa.

What Spanish does not normally say here is:

• Si el proyector no funcionará... ❌

Usaré is the first-person singular future of usar, meaning I will use.

The speaker is talking about what they will do in response to a possible situation:

• If the projector doesn’t work, I will use the board.

So the structure is:

• Si + present tense
• future tense in the main clause

That is a very common pattern for real future conditions in Spanish.

Because usaré expresses a real, likely response to a possible situation.

• usaré = I will use
• usaría = I would use

Usaría would sound more hypothetical or dependent on another condition. For example:

• Si el proyector no funcionara, usaría la pizarra.
• If the projector didn’t work, I would use the board.

That version is more hypothetical or less direct. In your sentence, the speaker is simply stating a normal future plan, so usaré fits better.

Spanish often leaves out subject pronouns because the verb ending already shows who the subject is.

Here, usaré clearly means I will use, so yo is not necessary.

• usaré = I will use
• yo usaré = also possible, but more emphatic

You might include yo only if you want contrast or emphasis:

• Si el proyector no funciona, yo usaré la pizarra y tú puedes explicar sin él.

Funciona comes from funcionar, meaning to function / to work.

So el proyector no funciona means:

• the projector doesn’t work
• the projector isn’t working

For machines, devices, and systems, funcionar is very common in Spanish.

Examples:

• Mi móvil no funciona. = My phone isn’t working.
• La impresora funciona bien. = The printer works well.

In Spain, pizarra usually means a board used for writing in class, which could be translated as:

• blackboard
• whiteboard
• sometimes simply board

In modern classrooms, people often still say pizarra even if it is technically a whiteboard rather than an old-style blackboard.

So the best English translation depends on context, but board is often the safest general meaning.

Spanish usually uses articles more often than English.

Here:

• el proyector = the projector
• la pizarra = the board

In this sentence, the speaker is probably referring to specific classroom objects, so the definite articles are natural.

Spanish sounds incomplete without them in many cases:

• Si proyector no funciona... ❌
• Si el proyector no funciona... ✅

Also, the articles show grammatical gender:

• el for masculine nouns like proyector
• la for feminine nouns like pizarra

Yes. That is completely correct.

Both of these mean the same thing:

• Si el proyector no funciona, usaré la pizarra.
• Usaré la pizarra si el proyector no funciona.

The difference is mainly one of focus or style:

• Starting with Si... puts the condition first.
• Starting with Usaré... puts the action first.

One small punctuation note:

• If the si-clause comes first, you usually write a comma:
  Si el proyector no funciona, usaré la pizarra.
• If it comes second, no comma is normally needed:
  Usaré la pizarra si el proyector no funciona.

In Spanish, no normally goes before the conjugated verb.

So:

• no funciona = doesn’t work

This is the normal order:

• No tengo tiempo. = I don’t have time.
• No entiendo. = I don’t understand.
• El proyector no funciona. = The projector doesn’t work.

Putting no after the verb is not correct in standard Spanish.

Not in this sentence as it stands.

With a real, possible condition about the future, Spanish uses:

• si + present indicative
• then a future or other main-clause tense

So:

• Si el proyector no funciona, usaré la pizarra. ✅

The subjunctive can appear in more hypothetical or unreal situations, but usually in the imperfect subjunctive after si, for example:

• Si el proyector no funcionara, usaría la pizarra.

That means something like:

• If the projector didn’t work, I would use the board.

So learners often need to remember:

• si + present for real future possibilities
• si + imperfect subjunctive for more hypothetical situations

Yes. That would also be natural.

• usaré la pizarra = I will use the board
• voy a usar la pizarra = I’m going to use the board

Both are common in everyday Spanish. The future form usaré can sound slightly more formal, concise, or written, while voy a usar can sound a bit more conversational.

So this is also fine:

• Si el proyector no funciona, voy a usar la pizarra.

Usaré has a written accent because the stress falls on the final syllable: u-sa-RÉ.

The accent mark helps show the correct stress and also distinguishes it from other forms.

Compare:

• usaré = I will use
• use = a different verb form, from the subjunctive or formal command context

So the accent is important both for pronunciation and for identifying the correct form.