El profesor trabaja en el laboratorio por la mañana.

In Spanish, singular countable nouns almost always need an article (like el, la, un, una) unless there’s a special reason to omit it.

So:

• El profesor = the professor / the teacher
• Profesor on its own sounds incomplete in this kind of sentence.

Compare:

• El profesor trabaja en el laboratorio. – The teacher works in the lab.
• Profesor, una pregunta. – Professor, a question. (here it’s used like a form of address, so no article)

In your sentence, you’re talking about “the professor” as a person who has that role, so you need el.

Yes. In Latin America, profesor / profesora is commonly used for:

• School teachers (elementary, middle, high school)
• College or university instructors
• Tutors, sports coaches, music teachers, etc., depending on context

So el profesor often just means the teacher, not necessarily a high-level university professor like in English. Context usually tells you what kind of “teacher” it is.

Spanish normally does not use subject pronouns (yo, tú, él, etc.) when the verb ending already tells you who is doing the action.

• Trabaja already shows it’s he / she / usted.
• Adding él is only needed for emphasis or contrast:
  
  • Él trabaja en el laboratorio, no en la oficina. – He works in the lab, not in the office.

You never say Él profesor. Él is a pronoun (he), and el is the article (the).
Correct: Él trabaja… or El profesor trabaja…

Trabaja is the 3rd person singular form of trabajar (to work) in the present tense:

• yo trabajo – I work
• tú trabajas – you work
• él / ella / usted trabaja – he / she / you (formal) work

Since the subject is el profesor (he), we must use trabaja.

• trabajar is the infinitive (to work), not correct here as a main verb.

Spanish simple present can cover both English ideas:

• El profesor trabaja en el laboratorio por la mañana. can mean:
  • The professor works in the lab in the morning. (habitual action)
  • In some contexts, also The professor is working in the lab this morning (though the progressive is clearer for “right now / currently”).

If you want to emphasize “right now / currently,” you can use the progressive:

• El profesor está trabajando en el laboratorio. – The professor is working in the lab (right now / currently).

Your sentence is read most naturally as a habitual routine.

• en = in / at (location)
• a = to (direction / movement)

In your sentence, you’re saying where he works, not where he goes:

• El profesor trabaja en el laboratorio. – The professor works in the lab.
• El profesor va al laboratorio. – The professor goes to the lab.

So en el laboratorio is correct for a location where the action happens.

Yes, but it changes the meaning slightly:

• en el laboratorio – in the laboratory (a specific lab, known from context)
• en un laboratorio – in a laboratory / in a lab (not specified which one)

If you’re talking about his usual workplace in a school or university, en el laboratorio is more natural.

Both are heard in Latin America, but there are preferences:

• por la mañana – widely used and very standard:
  
  • in the morning / during the morning
• en la mañana – also common, especially in parts of Latin America (e.g., some areas of Mexico, the Caribbean, etc.), with the same basic meaning.

In this sentence, por la mañana feels very neutral and natural everywhere.

Subtle nuance:

• por la mañana emphasizes “during that time period in general.”
• en la mañana can sound a bit more like “at some point in the morning,” depending on context.

For learning purposes, por la mañana is a very safe choice.

Spanish uses the definite article (la) with parts of the day:

• la mañana – the morning
• la tarde – the afternoon
• la noche – the night

With por, the usual expressions are:

• por la mañana – in the morning
• por la tarde – in the afternoon
• por la noche – at night

Saying por mañana alone is not correct for “in the morning.”

Context and the article tell you:

• la mañana = the morning
• mañana without article often = tomorrow

So:

• por la mañana – in the morning
• hasta mañana – see you tomorrow

In your sentence, la clearly shows it’s “morning,” not “tomorrow.”

Yes, that’s grammatically correct and used in many parts of Latin America:

• El profesor trabaja en el laboratorio en la mañana. – The professor works in the lab in the morning.

However, por la mañana is more idiomatic and slightly more common in many regions. If you’re not sure, prefer por la mañana.

Yes. Spanish word order is flexible for emphasis or style:

• El profesor trabaja en el laboratorio por la mañana.
• Por la mañana, el profesor trabaja en el laboratorio.

Both are correct and natural.
Putting Por la mañana at the beginning emphasizes the time: As for the mornings, that’s when he works in the lab.

The feminine form is:

• la profesora – the (female) teacher / professor

So you could say:

• La profesora trabaja en el laboratorio por la mañana.

The rest of the sentence stays the same; only the article and noun change gender.

Spanish words ending in a consonant other than n or s are stressed on the last syllable by default, without adding an accent mark.

• pro-fe-SOR ends in r, so it’s naturally stressed on -sor.
• No written accent is needed.

Compare:

• lápiz – needs an accent because stress is not on the expected syllable.
• profesor – follows the normal rule, so no accent.

Approximate pronunciation (Latin American standard):

• trabaja: trah-BAH-hah

  • tra like “tra” in “traffic” (short)
  • ba like “ba” in “bar”
  • ja like English “ha,” but with a stronger h sound from the throat

• laboratorio: lah-boh-rah-TOH-ryoh

  • la – “la” as in “lava”
  • bo – “bo” as in “boat” (short)
  • ra – rolled or tapped r
  • to – stressed syllable: TOH
  • rio – “ryoh” (the r is tapped)

Stress:

• trabaja – on BA: tra-BA-ja
• laboratorio – on TO: la-bo-ra-TO-rio