Learn Hardcore Turkish: Bu akşam planımız belli. - Our plan for this evening is clear.

Turkish often drops the verb “to be” in the present tense for noun/adjective predicates. This is a nominal sentence: the predicate is the adjective belli (“clear/settled”), so “is” is simply understood. You could add the copular suffix for formality or emphasis: Bu akşam planımız bellidir, but everyday speech prefers the zero-copula form.

What exactly does belli mean here? Are there close alternatives?

belli: clear, evident, known, set/decided. Here: “set/decided.”
kesin: definite/certain (stronger: no doubt, finalized). Bu akşam planımız kesin suggests it’s locked in.
net: clear-cut/explicit, not vague.
açık: “open/clear,” often about understandability or transparency.
belirli: specific/particular (more attributive: belirli bir plan “a specific plan”). A near-synonymous rewrite would be Bu akşam planımız kesin/net. Nuance changes slightly.

Why is planımız singular when English often says “our plans”?

Turkish doesn’t need a plural here; the singular can convey the general idea of “what we’re doing.” If you truly mean multiple distinct plans, use the plural: planlarımız. For example:

Singular (general): Bu akşam planımız belli. = Our plan/what we’ll do is set.
Plural (several items): Bu akşam planlarımız belli. = Our plans (several) are set.

How is planımız formed? What does the suffix mean?

Root: plan (plan)
Possessive suffix 1st person plural: -ımız/-imiz/-umuz/-ümüz (vowel harmony)
Because the root has a back vowel (a), you get plan-ımız → planımız = “our plan.” Pronunciation tips:
ı (dotless i) is a close back unrounded vowel; think a relaxed “uh” produced further back.
Stress typically falls near the end: pla-na-MIZ.

Do I need to say bizim planımız, or is planımız enough?

planımız already means “our plan.” Adding bizim (“our”) is optional and adds emphasis/contrast:

Neutral: Bu akşam planımız belli.
Emphatic/contrastive: Bizim planımız belli (ama sizin değil). = Our plan is set (but yours isn’t).

Can I say Bu akşamki planımız belli? What does -ki do?

Yes. -ki turns time/space phrases into adjectives meaning “of/for that time/place.”

Bu akşam planımız belli = Tonight, our plan is set. (Common, colloquial.)
Bu akşamki planımız belli = Our plan for tonight is set. (-ki makes the “for tonight” relationship explicit.)

Can I move bu akşam elsewhere? Does the meaning change?

Word order affects what “bu akşam” attaches to.

Default/topic-first: Bu akşam planımız belli. Usually heard as “Our plan for tonight is set.”
If you say Planımız bu akşam belli, it tends to mean “Our plan becomes clear tonight” (time of becoming clear), not “our plan for tonight.”
Planımız belli bu akşam is possible in speech for end-focus on “tonight,” but the default, most natural order is the original.

How do I negate it?

Use değil to negate nominal/adjectival predicates:

Bu akşam planımız belli değil. = Our plan for tonight isn’t set. For a slightly more formal tone: belli değildir.

What’s the difference between belli and belli oldu?

belli: a current state (“is clear”).
belli oldu: change-of-state (“became clear,” “has just become clear”). Examples:
Bu akşam planımız belli. = It’s (already) clear.
Bu akşam planımız belli oldu. = It has become clear (just now/recently).

How do I turn it into a yes/no question?

Add the question particle mi (harmonizes as mi/mı/mu/mü and is written separately):

Bu akşam planımız belli mi? = Is our plan for tonight set?

Does bu akşam mean “tonight” or “this evening”? How is it different from bu gece?

bu akşam: this evening (roughly early evening to around bedtime).
bu gece: tonight/late night (after dark, later hours). English “tonight” can map to either; choose based on whether you mean evening (akşam) or the late-night period (gece).

What’s the difference between planımız belli and planımız var?

planımız belli: the plan is clear/decided (content settled).
planımız var: we have a plan (existence), not necessarily specified or decided. You can also say the opposite with existence: Bu akşam planımız yok = We don’t have any plans for tonight.

Are there any agreement markers on belli for number or gender?

No. Turkish adjectives don’t agree in gender or number. belli stays the same whether the subject is singular or plural:

Planımız belli.
Planlarımız belli.

Can I just say Planımız belli and omit bu akşam?

Yes. Planımız belli = “Our plan is set.” Adding bu akşam limits it to the time frame of tonight. If you want to keep the “for tonight” sense while sounding tight and natural, Bu akşamki planımız belli is also great.