En caso de que olvides la tilde, revisa la última sílaba antes de entregar el ejercicio.

Both can mean something like if, but they are not exactly the same.

• Si is the basic word for if.
• En caso de que means in case or in the event that, so it sounds a bit more cautious or formal.

Here, en caso de que olvides la tilde suggests a possible situation the reader should be prepared for.

Compare:

• Si olvidas la tilde, revisa la última sílaba. = If you forget the accent mark, check the last syllable.
• En caso de que olvides la tilde, revisa la última sílaba. = In case you forget the accent mark, check the last syllable.

The second version feels a little more like an instruction or precaution.

Because en caso de que normally triggers the subjunctive.

The speaker is not saying that the person definitely forgets the accent mark. It is only a possible situation, so Spanish uses the subjunctive to show uncertainty, possibility, or hypothesis.

That is why you get:

• en caso de que olvides

and not:

• en caso de que olvidas

The indicative olvidas would sound wrong here in standard Spanish.

Olvides is the present subjunctive, tú form, of olvidar.

Quick breakdown:

• infinitive: olvidar
• present indicative tú: olvidas
• present subjunctive tú: olvides

This change from -as to -es is normal for -ar verbs in the present subjunctive.

Examples:

• hablas → hables
• estudias → estudies
• olvidas → olvides

Spanish often leaves out subject pronouns because the verb form already tells you who the subject is.

So in this sentence:

• olvides already means you forget
• revisa already means check addressed to you

Adding tú is possible, but usually unnecessary unless you want emphasis or contrast.

For example:

• En caso de que tú olvides la tilde...

This sounds more emphatic, as if contrasting you with someone else.

It is a command.

Revisa is the tú affirmative imperative of revisar, meaning check or review.

So the sentence is giving an instruction:

• revisa la última sílaba = check the last syllable

If it were more formal, it would be:

• revise la última sílaba for usted

And for plural you in Spain:

• revisad la última sílaba for vosotros
• revisen la última sílaba for ustedes

Because the subject is the same in both parts of the sentence.

The implied subject of revisa is you, and the implied subject of entregar is also you. When the subject stays the same, Spanish usually uses:

• antes de + infinitive

So:

• antes de entregar el ejercicio = before handing in the exercise

If the subject were different, Spanish would normally use antes de que + subjunctive.

Example:

• Revisa la última sílaba antes de que el profesor recoja el ejercicio.

Here the subject changes:

• you check it
• the teacher collects it

So antes de que is needed.

Here tilde means the written accent mark, like the mark in última or sílaba.

In English grammar terms, this is usually called an accent mark. In Spanish, tilde is the precise word for the written mark.

This is important because in Spanish:

• acento can refer to the spoken stress
• tilde refers to the written accent mark

So:

• sílaba tónica = stressed syllable
• tilde = the written mark placed on a vowel

In this sentence, the person is being told not to forget to write that mark.

Because sílaba is a feminine noun:

• la sílaba

Adjectives in Spanish usually agree with the noun in gender and number, so:

• la última sílaba
• la primera sílaba
• la sílaba tónica

Since sílaba is singular and feminine, última must also be singular and feminine.

In a school context, entregar el ejercicio usually means to hand in the exercise, turn in the assignment, or submit the work.

So entregar is not just a general deliver here. It has a very common classroom meaning:

• Voy a entregar el ejercicio. = I’m going to hand in the exercise.
• ¿Has entregado la tarea? = Have you handed in the homework?

In Spain, this is a very natural way to talk about submitting schoolwork.

Yes. Literally, it means the last syllable.

In this sentence, the idea is probably that checking the final syllable can help you verify whether a written accent mark is needed. So it is a proofreading instruction.

Related useful terms are:

• última sílaba = last syllable
• penúltima sílaba = second-to-last syllable
• antepenúltima sílaba = third-to-last syllable

These are important in Spanish spelling because accent rules depend on where the stress falls.

Yes. Both are natural, but they are slightly different in structure.

• olvidar la tilde = literally forget the accent mark
• olvidar poner la tilde = forget to put the accent mark

The second version is a little more explicit, because it clearly states the action of adding the accent mark.

So these are both possible:

• En caso de que olvides la tilde...
• En caso de que olvides poner la tilde...

The original version is shorter and perfectly normal.

If you were speaking formally to one person, you would use usted forms:

• En caso de que olvide la tilde, revise la última sílaba antes de entregar el ejercicio.

Changes:

• olvides → olvide
• revisa → revise

If you were speaking to a group in Spain using vosotros, it would be:

• En caso de que olvidéis la tilde, revisad la última sílaba antes de entregar el ejercicio.

So the original sentence is informal singular, addressed to tú.