Deneme süresi üç ay sürecek.

Because deneme süresi is a Turkish noun compound. In this pattern, the second noun usually takes the 3rd person possessive/compound suffix.

So:

• deneme = trial, testing
• süre = duration, period
• süre-si = its duration / duration of

Together, deneme süresi means trial period or probation period. In English we do not show this structure the same way, so it can feel strange at first.

Grammatically, yes, it is the same suffix shape as a 3rd person possessive ending, but in phrases like this it often functions as part of a noun-compound structure, not as literal possession in the everyday sense.

So deneme süresi is not necessarily emphasizing its period in a strong possessive way. It is simply the normal Turkish way to say trial period.

The s is a buffer consonant:

• süre + i would be awkward
• so Turkish uses süre-si

Sürecek means will last.

It comes from the verb sürmek, which can mean things like:

• to last
• to continue
• in other contexts, even to drive or to spread/apply

Here it clearly means to last.

Formation:

• sür- = verb stem
• -ecek = future tense suffix

So sürecek = it will last.

Because Turkish usually expresses the future with a verb ending, not with a separate helper word like English will.

So instead of saying something like will last, Turkish builds the future directly into the verb:

• sürer = lasts / will last in some contexts
• sürecek = will last

This is very common in Turkish grammar. Tense is often built into the verb itself.

Because Turkish often uses a bare time expression to show duration.

So:

• üç ay sürecek = it will last three months
• iki gün bekledim = I waited two days
• bir yıl yaşadı = he/she lived for one year

English often needs for, but Turkish usually does not.

Yes, you could. Boyunca means something like throughout / for the duration of.

So:

• üç ay sürecek = will last three months
• üç ay boyunca sürecek = will last for three months / throughout three months

The version without boyunca is more direct and very natural here. Adding boyunca can sound slightly more explicit or emphatic.

Because Turkish normally prefers verb-final word order.

This sentence follows a very typical pattern:

• Deneme süresi = subject/topic
• üç ay = duration
• sürecek = verb

So the neutral order is: Deneme süresi üç ay sürecek.

This is one of the biggest differences from English.

Yes. The subject is deneme süresi.

The sentence is basically saying: The trial period + will last + three months

Turkish does not need a separate pronoun like it here, because the subject noun phrase is already present.

It can vary by context.

Deneme can mean:

• trial
• test
• attempt
• practice
• sometimes part of a phrase meaning probation

So deneme süresi could mean:

• trial period
• testing period
• probation period

In a work or contract context, probation period is often the most natural English meaning.

Yes, Turkish word order is flexible, but changing it usually changes the focus or emphasis.

For example:

• Deneme süresi üç ay sürecek. = neutral
• Üç ay sürecek deneme süresi. = possible in a different sentence role, but not the same neutral standalone statement
• Üç ay deneme süresi sürecek. = unnatural or confusing

So for a simple statement, Deneme süresi üç ay sürecek is the best standard order.

Because Turkish has no articles like English a/an/the.

Whether English uses a or the depends on context, not on a separate Turkish word here.

So Deneme süresi üç ay sürecek could be translated as:

• The trial period will last three months
• sometimes A trial period will last three months

In most real contexts, the trial period is the most natural translation.