El rodillo alisa la arcilla.

Alisar is the infinitive, equivalent to to smooth / to flatten.

In the sentence, you need a conjugated verb, so Spanish uses alisa, which is the third-person singular present tense form:

• yo aliso = I smooth
• tú alisas = you smooth
• él / ella / usted alisa = he / she / you smooths

Since el rodillo is he/it grammatically, alisa is the correct form.

It is the present simple.

So El rodillo alisa la arcilla is in the same basic tense as:

• The roller smooths the clay
• The rolling pin smooths the clay

Spanish uses the present tense here just like English does for a general statement or a description of what something does.

Because rodillo is a masculine singular noun, so it takes the masculine singular definite article el.

• el rodillo
• un rodillo

A lot of Spanish nouns ending in -o are masculine, and rodillo follows that common pattern.

Because arcilla is a feminine singular noun, so it takes la.

• la arcilla
• una arcilla

Also, Spanish often uses the definite article more than English does, especially with materials or substances. So where English might sometimes just say clay, Spanish can naturally say la arcilla.

Because Spanish usually does not need a subject pronoun when the subject is already clear.

Here, the subject is explicitly stated as el rodillo, so there is no need to add anything like it.

Spanish is a pro-drop language, which means subject pronouns are often omitted when they are unnecessary.

For example:

• Alisa la arcilla = It smooths the clay / He/She smooths the clay, depending on context
• El rodillo alisa la arcilla = the noun itself makes the subject clear

A good clue is the verb and the normal word order.

Spanish commonly follows:

• subject + verb + object

So in:

• El rodillo = subject
• alisa = verb
• la arcilla = direct object

In other words, the roller / rolling pin performs the action, and the clay receives the action.

Because the personal a is normally used with people and sometimes pets or very personified beings, not ordinary things or materials.

So:

• Veo a María = I see María
• Veo el rodillo = I see the roller
• El rodillo alisa la arcilla = no a, because arcilla is a thing

Since la arcilla is an inanimate material, no personal a is used.

Rodillo can refer to a roller or a rolling pin, depending on context.

The basic idea is a cylindrical tool that rolls. In different situations, it might mean:

• a kitchen rolling pin
• a craft or pottery roller
• a paint roller in other contexts

So the precise English word depends on what kind of scene you are talking about. In this sentence, if the context is clay or pottery, roller is often the most natural choice.

Not exactly, though they can overlap.

• alisar = to smooth, to make a surface even or less rough
• aplanar = to flatten, to make something flatter

With clay, both might make sense depending on context, but alisar focuses more on smoothing the surface.

So if the sentence uses alisar, the emphasis is on making the clay smooth.

A useful approximate pronunciation is:

• ro-DEE-yo in many speakers’ Spanish

A few points:

• r in rodillo is a soft tapped r
• ll in most modern Spanish is pronounced like y in yes
• the stress falls on di: ro-DI-llo

In parts of Spain, the ll sound may vary slightly, but pronouncing it like y is a good standard choice for learners.

In Spain, a good approximation is:

• ar-THEE-ya in much of Spain

Why?

• ci before a/o/u would not happen, but here the c is before i, so in most of Spain it sounds like the th in thin
• ll is usually like y
• the stress is on ci: ar-CI-lla

In Latin America, many speakers would pronounce it more like ar-SEE-ya. But for Spain, ar-THEE-ya is the usual model.

The normal, most neutral order is:

• El rodillo alisa la arcilla

Spanish word order is more flexible than English, but changing it usually changes the emphasis.

For example, you might see:

• La arcilla la alisa el rodillo

That structure is possible, but it sounds more marked and emphatic. For a learner, the original sentence is the best standard pattern to use.

Yes, alisar is a regular -ar verb.

Its present tense forms are:

• yo aliso
• tú alisas
• él / ella / usted alisa
• nosotros alisamos
• vosotros alisáis
• ellos / ellas / ustedes alisan

So if you already know regular -ar verb patterns, this verb behaves just as expected.

Because Spanish often uses the definite article in places where English would not.

English might say:

• Clay is soft
• The roller smooths clay

But Spanish often prefers:

• La arcilla es blanda
• El rodillo alisa la arcilla

This does not always mean a very specific piece of clay. It can simply be the natural Spanish way to refer to the material in context.