Learn Hardcore Turkish: Umarım siz de bize katılırsınız.

Umarım means I hope and can directly introduce a clause. Turkish doesn’t need a that/ki here: Umarım siz de bize katılırsınız is complete. You can say Umarım ki for emphasis or style, but many consider the ki redundant; both forms are common and acceptable.

Why is katılırsınız used (the -r aorist) instead of a clear future like katılacaksınız?

Katılırsınız is the aorist (general/habitual), but with verbs of wishing or thinking (like umarım), Turkish often uses the aorist to mean a polite, non-committal future: I hope you’ll join. Katılacaksınız is a definite, scheduled future (You are going to join), which can sound too firm with umarım. The aorist here keeps the hope soft and less imposing.

Could I say katılıyorsunuz instead?

Not for a future hope. Katılıyorsunuz is present continuous (you are joining/attending now) or a near-term arrangement being carried out. With a hope about a future action, prefer katılırsınız (soft future) or katılacaksınız (definite future) depending on nuance.

What does siz de mean? Does de modify you or us?

De is the additive clitic meaning also/too, and it modifies the word it follows. In siz de, it means you too (as well as others). If you said bize de, it would mean to us too (as well as to others). So word placement changes what is being marked as “also.”

Is this de the same as the locative suffix -de/-da?

No. There are two things that look similar:

The additive clitic de/da = also/too. It’s written separately (e.g., siz de) and always uses d- (never t-).
The locative suffix -de/-da/-te/-ta = in/at/on, written attached (e.g., sizde = on/with you). Note the difference: siz de (you too) vs sizde (on you/at your place, or you have).

How do I choose de vs da here?

The additive clitic follows vowel harmony: after a front-vowel word use de; after a back-vowel word use da. Since siz has the front vowel i, it’s siz de (not siz da). Also, as a clitic, it never turns into te/ta.

Why is it bize and not bizi or bizimle?

The verb katılmak takes the dative case: join someone/something = X’e katılmak. Hence bize (to us). Using bizi (accusative) is ungrammatical with katılmak, and bizimle (with us) sounds off because the verb prefers dative rather than the comitative -le. Compare:

Bize katılın = Join us.
Bizimle gelin = Come with us. (Different verb, different case choice.)

Can I drop the pronoun siz?

Yes. Turkish doesn’t need subject pronouns when the verb ending shows person/number. Umarım bize katılırsınız is perfectly natural. Keeping siz adds emphasis (you in particular) or politeness/clarity.

How do I make it informal singular?

Change the person ending to 2nd singular: Umarım bize katılırsın. You can also drop the pronoun: Umarım bize katılırsın. If you keep it, use sen: Umarım sen de bize katılırsın.

What’s the exact breakdown of katılırsınız?

katıl- (verb stem: join)
-ır- (aorist marker; harmonizes as ır/ir/ur/ür)
-sınız (2nd person plural/formal singular ending; harmonizes as sınız/siniz/sunuz/sünüz) So: katıl-ır-sınız. The last vowel is back, so we get -ır-, -sınız.

And what about Umarım morphologically?

From the verb ummak (to hope). In the aorist, the stem surfaces as umar-; with the 1st person singular ending -ım, you get umarım = I hope. You’ll also hear Umuyorum (ki)… using the -yor progressive of ummak; both are natural.

Is there any nuance between Umarım and İnşallah?

Umarım is secular/neutral: I hope.
İnşallah literally means God willing and is very common in everyday speech; it can sound more casual or culturally/religiously colored, though many people use it regardless of religiosity. Both can fit here: İnşallah siz de bize katılırsınız.

Are there other polite or alternative ways to express the same idea?

Ability focus: Umarım bize katılabilirsiniz. (I hope you can join us.)
Conditional + warm follow-up: Katılabilirseniz çok seviniriz. (We’d be very happy if you can join.)
Polite imperative: Lütfen bize katılın. (Please join us.)
Invitation flavor: Sizi aramızda görmek isteriz. (We’d like to see you among us.)

Any punctuation or capitalization tips here?

No comma is needed after Umarım; Umarım siz de… is standard. Siz is normally not capitalized; uppercase Siz appears only in very formal letters to show extra respect.