Marca el paso; si no, repítelo.

Yes. Marca is the affirmative tú command of marcar.

For most -ar verbs, the affirmative tú command is the same as the él/ella/usted present-tense form:

• marcar → marca
• hablar → habla
• tomar → toma

So Marca el paso is giving a command to one person in the informal tú form.

Spanish often uses the definite article more than English does. So el paso is completely natural here.

In English, we might sometimes leave the article out in short commands, but Spanish often keeps it:

• abre la puerta
• levanta la mano
• marca el paso

So this is not unusual grammar; it is just how Spanish commonly phrases things.

This is a very common question.

Here, si no is written as two words and means something like if not.

• si = if
• no = not

So:

• si no, repítelo = if not, repeat it

This is different from sino as one word, which usually means but rather / except in contrast structures.

Compare:

• No quiero té, sino café. = I don’t want tea, but rather coffee.
• Hazlo bien; si no, repítelo. = Do it properly; if not, repeat it.

So in your sentence, si no is definitely the two-word version.

The semicolon links two closely related parts:

• Marca el paso
• si no, repítelo

It works a bit like a strong comma or a light full stop. It shows that the second part depends on the first one.

You could think of it as:

• Do X; if not, do Y.

In everyday writing, some people might use a comma instead, but the semicolon is perfectly natural and helps separate the two instructions clearly.

Because in Spanish, with an affirmative command, object pronouns are usually attached to the end of the verb.

So:

• repite = repeat
• lo = it
• repítelo = repeat it

This is normal with affirmative imperatives:

• hazlo = do it
• míralo = look at it
• dímelo = tell me it

By contrast, with negative commands, the pronoun goes before the verb:

• No lo repitas = Don’t repeat it

So repítelo is one word because it is an affirmative command.

The accent mark is there to keep the correct stress after the pronouns are attached.

Without pronouns:

• repite

When lo is added:

• repítelo

Spanish adds the written accent to preserve the original stress pattern. This is very common with commands plus pronouns:

• dime → dímelo
• escribe → escríbelo
• repite → repítelo

So the accent is not optional; it shows where the stress should stay.

Lo is a direct object pronoun meaning it.

In this sentence, it refers back to whatever should be repeated. Depending on the context, that could be the action, the step, the phrase, the beat, etc.

A learner often asks why it is lo and not la. The answer is that the pronoun agrees with the grammatical gender of the thing being replaced:

• masculine singular noun → lo
• feminine singular noun → la

So if it refers back to el paso, then lo makes sense because paso is masculine.

Yes. Repítelo comes from the verb repetir, and here it is also an affirmative tú command.

The basic command is:

• repite = repeat

Then the pronoun is attached:

• repite + lo → repítelo

So both verbs in the sentence are commands addressed to one person informally.

You would use the usted command forms instead:

• Marque el paso; si no, repítalo.

Changes:

• marca → marque
• repítelo → repítalo

That is because usted commands use the present subjunctive forms.

So:

• tú: Marca el paso; si no, repítelo.
• usted: Marque el paso; si no, repítalo.

As written, no. It is singular informal, so it is directed at one person.

In Spain, if you wanted to speak to more than one person informally, you would usually use vosotros:

• Marcad el paso; si no, repetidlo.

That is the standard Spain form for informal plural commands.

So the original sentence is clearly singular tú, not plural.

Because Spanish handles pronouns differently in negative commands.

• Affirmative command: pronoun goes after the verb
  
  • Repítelo
• Negative command: pronoun goes before the verb
  
  • No lo repitas

So no repítelo is not correct Spanish.

This is a very important pattern to learn:

• Hazlo / No lo hagas
• Escríbelo / No lo escribas
• Repítelo / No lo repitas

The sentence itself is standard Spanish and would be understood broadly, not just in Spain.

What may feel especially relevant for a learner of Spain Spanish is how the plural would work:

• in Spain: vosotros → marcad, repetidlo
• in most of Latin America: ustedes → marquen, repítanlo

But the original singular version with tú is standard everywhere.

Yes, that can confuse learners at first.

Spanish often has forms that look identical but do different jobs depending on context:

• la marca = the brand / the mark
• marca = he/she marks, you mark (formal), or mark! as a tú command depending on context

In Marca el paso, the sentence structure makes it clear that this is a verb in command form, not a noun.