La buena caligrafía hace que la profesora entienda cada renglón sin esfuerzo.

Because hace que often triggers the subjunctive when one thing causes another person to do something.

Here, the structure is:

La buena caligrafía hace que + la profesora + entienda...

So the idea is:

• The good handwriting causes
• the teacher to understand

That is why Spanish uses entienda, the present subjunctive of entender.

Compare:

• La profesora entiende cada renglón. = The teacher understands every line.
  
  • This is just a statement, so indicative: entiende.
• La buena caligrafía hace que la profesora entienda cada renglón. = The good handwriting makes the teacher understand every line.
  
  • This uses hace que, so subjunctive: entienda.

In this sentence, hace que means makes or causes.

So:

• La buena caligrafía hace que... = Good handwriting makes it so that...
• More naturally in English: Good handwriting makes the teacher understand...

It is a very common Spanish structure for expressing cause:

• Eso hace que me preocupe. = That makes me worry.
• La lluvia hace que el partido sea difícil. = The rain makes the match difficult.

So hacer que + subjunctive is a useful pattern to learn.

Yes — in this context, caligrafía is best understood as handwriting.

Although the literal cognate is calligraphy, in everyday Spanish caligrafía often refers to a person’s handwriting, especially in school or when talking about whether writing is neat and readable.

So:

• buena caligrafía = good handwriting
• mala caligrafía = bad handwriting

A native English speaker might expect something more artistic from calligraphy, but Spanish caligrafía is often much broader and more ordinary.

Spanish often uses the definite article more than English does.

Here, La buena caligrafía means something like:

• Good handwriting
• literally, the good handwriting

In Spanish, abstract or general ideas are often introduced with the definite article:

• La paciencia es importante. = Patience is important.
• La buena educación ayuda mucho. = Good manners / a good education helps a lot.
• La buena caligrafía... = Good handwriting...

So the article sounds natural in Spanish even if English would usually leave it out.

Because caligrafía is a feminine singular noun.

That means the adjective must agree with it:

• la caligrafía
• buena caligrafía

Spanish adjectives usually agree in gender and number with the noun:

• buen libro = good book
• buena idea = good idea
• buenas notas = good grades

Since caligrafía is feminine singular, buena is the correct form.

Renglón means line of writing — a line on a page.

So cada renglón means:

• each line
• every line

This word is especially used for written text on paper or in a notebook.

It is slightly more specific than línea, because línea can mean many kinds of line:

• a drawn line
• a line in geometry
• a telephone line
• a train line
• a line of text

But renglón clearly points to a written line of text.

Because cada is followed by a singular noun.

So you say:

• cada renglón = each line
• cada palabra = each word
• cada día = each day

Not:

• cada renglones
• cada palabras
• cada días

Even though English often uses every line or each line, Spanish keeps the noun singular after cada.

Sin esfuerzo means without effort or effortlessly.

It is a very common expression:

• leer sin esfuerzo = to read without effort
• resolverlo sin esfuerzo = to solve it without effort

There is no article because Spanish often uses sin + noun in a general sense:

• sin problema = without a problem / no problem
• sin miedo = without fear
• sin ayuda = without help
• sin esfuerzo = without effort

You could sometimes hear sin ningún esfuerzo for emphasis: without any effort at all.

Because in standard Spanish, a noun like profesora usually needs an article or some other determiner.

So Spanish normally says:

• la profesora = the teacher
• una profesora = a teacher
• mi profesora = my teacher

Just profesora by itself would usually sound incomplete in a sentence like this.

Here, la profesora suggests a specific teacher already known from context.

Possibly, but the meaning and feel would change a bit.

In Spain:

• profesora is a general word for female teacher
• maestra often suggests a primary-school teacher, though usage can depend on context

So la profesora is a broad, safe choice.

Also, profesor/profesora is very common in school and academic contexts in Spain.

Yes. It comes from the verb entender.

The present indicative forms are:

• entiendo
• entiendes
• entiende
• entendemos
• entendéis
• entienden

Notice the stem change:

e → ie

The present subjunctive is built from the yo form (entiendo), so you get:

• entienda
• entiendas
• entienda
• entendamos
• entendáis
• entiendan

So entienda is the correct subjunctive form for la profesora.

Yes, but it would sound slightly different.

For example:

• La profesora entiende cada renglón sin esfuerzo gracias a la buena caligrafía.

This means essentially the same thing:
The teacher understands every line effortlessly thanks to the good handwriting.

The difference is in focus:

• La buena caligrafía hace que... puts the spotlight on the handwriting as the cause
• La profesora entiende... gracias a... puts the spotlight more on the teacher’s understanding

Both are natural, but the original sentence emphasizes the cause-effect relationship.

Renglón is perfectly understandable and natural for a line of writing.

Línea could also work in some contexts, but it is broader and less specific.

Compare:

• cada renglón = each written line
• cada línea = each line, but this could be more general

If the sentence is specifically about handwriting on a page, renglón is a very suitable choice.

A more literal translation would be:

The good handwriting makes it so that the teacher understands each line without effort.

But that is not the most natural English version.

A more natural translation is:

Good handwriting makes the teacher understand every line effortlessly.

This is a good example of how Spanish often uses a structure like hacer que + subjunctive, while English tends to use a simpler make + object + verb structure.