Trabajo ya sea hoy o mañana.

Here trabajo is the verb, not the noun. It is the first-person singular present form of trabajar, so it means I work or, depending on context, I’m working / I will work.

Spanish often allows this kind of present tense where English might prefer a future form, especially when the time is made clear by words like hoy or mañana.

As a noun, trabajo means work or job, but in this sentence the structure clearly points to the verb.

Because Spanish usually drops subject pronouns when the verb ending already shows who the subject is.

• trabajo = I work
• trabajas = you work
• trabaja = he/she/you formal works

So yo trabajo is possible, but trabajo by itself is completely normal. You would add yo only for emphasis, contrast, or clarity.

Ya sea ... o ... is a set expression that introduces alternatives. In English, it often corresponds to either ... or ... or sometimes whether it be ... or ....

So in this sentence, ya sea hoy o mañana presents two options:

• today
• tomorrow

It is a way of saying that one of those two possibilities applies.

Because sea is not the main verb of the sentence. The main verb is trabajo.

The word sea comes from ser, and in ya sea ... o ... it is part of a fixed expression. You do not translate it word-for-word as a normal standalone to be here. Instead, you should treat ya sea ... o ... as one unit meaning either ... or ....

So the structure is roughly:

• Trabajo = main action
• ya sea hoy o mañana = expression giving the alternatives

Yes. Sea is the present subjunctive form of ser.

That may look strange at first, but in this sentence it is best learned as part of the fixed pattern ya sea ... o .... The sentence does not mean that the main verb trabajo is subjunctive. Only sea is in that form because the expression itself uses it.

So you should not change trabajo to trabaje here.

It can absolutely be used with short elements like these.

In this sentence, hoy and mañana are time expressions, and ya sea ... o ... works fine with them. It can connect many kinds of things:

• nouns
• adjectives
• adverbs
• prepositional phrases
• full clauses

Examples:

• ya sea en casa o en la oficina
• ya sea hoy o mañana
• ya sea que venga o que no venga

So yes, using it with just hoy and mañana is normal.

It is grammatical, but it can sound a bit formal or careful because ya sea ... o ... is more elevated than simply using o by itself.

In everyday conversation, many speakers would more naturally say something like:

• Trabajo hoy o mañana.
• Voy a trabajar hoy o mañana.
• Trabajaré hoy o mañana.

The version with ya sea adds a more explicit either/or feel. So it is not wrong, but it may sound more formal than the simplest everyday option.

Spanish often uses the present tense for a planned or expected future action, especially when a time expression makes the timing clear.

So a present-tense verb can refer to the near future:

• Mañana salgo temprano.
• Esta noche cenamos afuera.

In the same way, trabajo can refer to a present or near-future action, depending on context.

If the speaker wants to sound more explicitly future-oriented, they could say:

• Trabajaré ya sea hoy o mañana.
• Voy a trabajar ya sea hoy o mañana.

Usually it presents alternatives, but whether it means exactly one or simply one of those possibilities depends on context.

In many real situations, ya sea ... o ... functions very much like either ... or ..., but Spanish does not always force a strict logical distinction. The sentence mainly tells you that the action will happen in one of those two time frames.

So the exact degree of exclusivity comes from the situation, not just from the grammar.

No. The most common pattern is simply:

• ya sea X o Y

So ya sea hoy o mañana is perfectly fine.

You can also repeat it for emphasis or rhythm:

• ya sea hoy o ya sea mañana

That version is possible, but it is usually less necessary and can sound heavier.

Yes. You could move the alternative phrase to the front for emphasis:

• Ya sea hoy o mañana, trabajo.

But that version sounds more marked and less neutral. The original order:

• Trabajo ya sea hoy o mañana.

keeps the main action first and then adds the alternatives. That is a very normal way to build the sentence.