La profesora escribió la medida exacta del rectángulo en la pizarra.

Profesora is the feminine form of profesor, meaning teacher. Since the sentence uses la profesora, it refers to a female teacher.

• el profesor = the male teacher
• la profesora = the female teacher

Spanish usually marks grammatical gender clearly in nouns referring to people.

Because La profesora is the subject: the person who performed the action.

In this sentence:

• La profesora = the subject
• escribió = the verb
• la medida exacta del rectángulo = what she wrote
• en la pizarra = where she wrote it

Spanish often follows the same basic order as English here: subject + verb + object + place.

Escribió is the preterite of escribir, the verb to write.

It means wrote in the sense of a completed action in the past.

• escribe = she writes / is writing
• escribía = she was writing / used to write
• escribió = she wrote

So this sentence describes a finished event: the teacher wrote something on the board.

The accent mark in escribió shows where the stress falls: on the last syllable, -bió.

It also helps distinguish the preterite form from other forms:

• escribio would be incorrect
• escribió = he/she wrote

Accent marks in Spanish are very important because they can change pronunciation and sometimes meaning or grammatical form.

Because medida is a feminine noun, so the article and adjective must agree with it.

• la medida = the measurement
• exacta = exact, matching the feminine noun

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

• el tamaño exacto
• la medida exacta

So exacta is feminine singular because medida is feminine singular.

Here medida most naturally means measurement or dimension.

So la medida exacta del rectángulo means something like:

• the exact measurement of the rectangle
• the exact dimensions of the rectangle depending on context

Spanish medida can mean:

• a measurement
• a dimension
• a measure
• sometimes even a step or action in other contexts

Here, because it refers to a rectangle, measurement is the best fit.

Because de + el contracts to del in Spanish.

So:

• de + el rectángulo → del rectángulo

This is a standard contraction:

• a + el → al
• de + el → del

Important: this contraction does not happen with la:

• de la pizarra, not dela pizarra

It means of the rectangle and specifies what the measurement belongs to.

So:

• la medida exacta = the exact measurement
• del rectángulo = of the rectangle

Together: la medida exacta del rectángulo = the exact measurement of the rectangle

This structure is very common in Spanish:

• la puerta de la casa = the door of the house
• el color del coche = the colour of the car

Because it adds location information: on the board / on the blackboard / on the whiteboard.

Spanish often places location phrases after the main object, just as English often does:

• The teacher wrote the exact measurement of the rectangle on the board.
• La profesora escribió la medida exacta del rectángulo en la pizarra.

You could move it for emphasis in some contexts, but the given order is the most neutral and natural.

In Spain, pizarra can refer to a classroom board in general. Depending on context, it may be translated as:

• blackboard
• chalkboard
• whiteboard
• simply board

The exact English translation depends on what kind of board is actually being used.

Because Spanish uses definite articles more regularly than English, and several nouns here are feminine singular:

• La profesora
• la medida exacta
• la pizarra

Each la means the, but it must agree with its noun:

• la profesora
• la medida
• la pizarra

This repetition is normal and natural in Spanish.

Because the personal a is mainly used before a specific human person as a direct object.

Here, the direct object is a thing:

• la medida exacta del rectángulo

So no a is used.

Compare:

• La profesora vio a María. = The teacher saw María.
• La profesora escribió la medida. = The teacher wrote the measurement.

Yes, but the meaning and usage change slightly.

• escribió = wrote; a finished past action
• ha escrito = has written

In many parts of Spain, pretérito perfecto (ha escrito) is common for recent past actions connected to the present. But escribió is also completely correct when talking about a completed event in the past.

So both are possible depending on context, but they are not always interchangeable.

Yes, that word order is possible.

• La profesora escribió la medida exacta del rectángulo en la pizarra.
• La profesora escribió en la pizarra la medida exacta del rectángulo.

Both are grammatical. The original version is a neutral way to present:

1. what she wrote
2. where she wrote it

The alternative puts a little more focus on where she wrote it.

A useful way to break it up is:

• La profesora = the teacher
• escribió = wrote
• la medida exacta = the exact measurement
• del rectángulo = of the rectangle
• en la pizarra = on the board

So the full structure is:

La profesora + escribió + la medida exacta del rectángulo + en la pizarra

Learning to spot these chunks makes long Spanish sentences much easier to understand.