Estudiar español cada día es mi objetivo principal.

Spanish often uses the infinitive (estudiar) as the subject of a sentence, where English uses a -ing form:

• Estudiar español cada día es mi objetivo principal.
  → Studying Spanish every day is my main goal.

If you said Estudio español cada día es mi objetivo principal, it would be ungrammatical because estudio is a conjugated verb (I study), not a noun-like form.

The infinitive estudiar acts like a noun here, similar to to study / studying used as a subject in English.

Yes, that word order is completely correct and very natural:

• Estudiar español cada día es mi objetivo principal.
• Mi objetivo principal es estudiar español cada día.

They mean the same thing.
The difference is only emphasis:

• Starting with Estudiar español cada día emphasizes the activity itself.
• Starting with Mi objetivo principal emphasizes the goal.

In Spanish, when you talk about a language in general as a direct object of certain verbs (like hablar, aprender, estudiar), you usually omit the article:

• Estudio español. = I study Spanish.
• Aprendemos francés. = We learn French.

You would normally see el español in other contexts, for example:

• El español es una lengua muy hablada.
  (Spanish is a widely spoken language.)

So here, Estudiar español (no article) is the most natural form.

Both usually mean every day and are interchangeable in most contexts:

• Estudio español cada día.
• Estudio español todos los días.

Nuance (very slight):

• cada día can sound a bit more like day after day / each single day, sometimes with a sense of regularity or even effort.
• todos los días is the most neutral, everyday way to say every day.

In your sentence, either one works fine.

Ser (es) and estar (está) are both “to be,” but they are used differently.

• Ser is used for essential characteristics, identity, definitions, and roles.
• Estar is used for temporary states, locations, and conditions.

Here, estudiar español cada día is identified as your main goal. It defines what your main goal is, so you use ser:

• Estudiar español cada día es mi objetivo principal.
  (Studying Spanish every day is my main goal.)

Using está here would be incorrect.

Spanish has two types of possessive forms:

1. Short (adjectival) forms: mi, tu, su, nuestro, etc.

   • Always placed before the noun.
   • Function like my, your, his/her in English.
   • Example: mi objetivo = my goal.

2. Long (pronominal) forms: mío, tuyo, suyo, nuestro, etc.

   • Usually placed after the noun or used alone.
   • Example:
     
     • Es mi objetivo. = It is my goal.
     • Es objetivo mío. = It is a goal of mine. (more emphatic / stylistic)
     • Es mío. = It is mine.

In front of a noun you normally use mi, not mío:
mi objetivo principal is correct; mío objetivo principal is wrong.

You can say principal objetivo, but it is less common and can sound more formal or emphatic depending on the context.

In everyday speech and writing:

• objetivo principal is the natural, default order:
  
  • Estudiar español cada día es mi objetivo principal.

Adjectives like principal often go after the noun in neutral statements. Putting it before the noun is more marked and can change the tone or emphasis.

Objetivo and meta are very close in meaning (goal, objective), but there’s a small nuance:

• objetivo: more neutral, slightly more “technical” or “business-like” in some contexts.
• meta: often used for personal goals, long-term ambitions, or milestones.

Both are fine here:

• Estudiar español cada día es mi objetivo principal.
• Estudiar español cada día es mi meta principal.

The difference is subtle; you can treat them as synonyms in this sentence.

Yes:

• Estudiar español diariamente es mi objetivo principal.

diariamente = daily.
Nuance:

• cada día / todos los días sound more conversational.
• diariamente sounds a bit more formal or written.

All are correct; choose based on style.

In Spanish, the gerund (forms like estudiando) is not normally used as a subject of the sentence.

• Estudiando español is a verbal form that usually expresses something ongoing (while studying Spanish, by studying Spanish, I am studying Spanish), not a noun-like action.

To make the action itself the subject (like studying Spanish), Spanish uses the infinitive:

• ✅ Estudiar español cada día es mi objetivo principal.
• ❌ Estudiando español cada día es mi objetivo principal.

Two different things are happening:

1. Día

   • The accent (´) marks the stressed syllable and sometimes distinguishes words that would otherwise be written the same.
   • día is stressed on dí-: DÍ-a.

2. Ñ in español

   • ñ is a separate letter in the Spanish alphabet, not just an n with a mark.
   • It represents a different sound, like the ny in canyon.
   • So español is pronounced roughly es-pa-NYOL.

Both marks are essential; without them, the words are either wrong or would be pronounced differently.

The sentence is neutral in terms of formality and sounds natural in Latin American Spanish:

• You can use it in casual conversation, in class, or even in a written text.
• There is no slang, and the vocabulary (estudiar, objetivo, principal) is standard and widely understood across Latin America.

In most of Latin America, people usually say español for the language:

• Estudiar español cada día… is the normal way.

castellano is also understood and used in some countries (like Argentina and parts of others), but español is the safest, most universally recognized choice across Latin America.