Learn Hardcore Ukrainian: Чия це сумка?

Because чия agrees with the grammatical gender and number of the noun сумка, which is feminine singular. The interrogative pronoun чий declines for gender/number:

masculine: чий (e.g., Чий це телефон?)
feminine: чия (Чия це сумка?)
neuter: чиє (Чиє це вікно?)
plural: чиї (Чиї це ключі?)

What is це doing here? Why not ця?

це is a demonstrative pronoun used in identifying statements/questions, roughly “this is/it is.”
ця is an attributive demonstrative meaning “this” used directly before a feminine noun: ця сумка = “this bag.”

So:

Чия це сумка? = “Whose bag is this?” (standard, very common)
Чия ця сумка? = also correct, more like “Whose is this bag?” with the bag explicitly identified as “this.”

Is Чия сумка? (without це) also correct?

Yes. Чия сумка? is perfectly natural and common, especially in short, context-heavy situations (e.g., pointing at a bag). Чия це сумка? is slightly more explicit when you’re indicating a particular object as “this.”

Why is there no word for “is”? Where is є?

In Ukrainian, the present-tense copula (є) is usually omitted in simple equational sentences. You typically do not say є here.

Natural: Чия це сумка?
Unnatural in everyday speech: Чия це є сумка? (you may see є in very formal definitions, but not in this question)

What case is сумка in, and why isn’t it genitive?

Сумка is in the nominative because the question is an identification: “This (thing) — whose bag?” In Ukrainian, both parts of such equations are in the nominative. To name the owner explicitly, you can use a genitive phrase:

Чия це сумка? — Це сумка Оксани. (genitive: “Oksana’s”)

How do I answer this question naturally?

With a possessive pronoun: Моя / твоя / його / її / наша / ваша / їхня.
- Example: Це моя сумка. or just Моя.
With a genitive name: Це сумка Оксани.
With a proper noun + possessive adjective (less common, more literary): Це Оксанина сумка.

How would the sentence change with different genders or plural?

Masculine noun: Чий це рюкзак? (“Whose backpack is this?”)
Neuter noun: Чиє це пальто? (“Whose coat is this?”)
Plural noun: Чиї це документи? (“Whose documents are these?”)

Can I change the word order? What about Ця сумка чия?, Це чия сумка?, or Чия сумка це?

Чия це сумка? — default, neutral.
Ця сумка чия? — also common and natural; topic (“this bag”) first.
Це чия сумка? — possible, often conveys surprise/annoyance (“Whose bag is this?!”).
Чия сумка це? — grammatical but uncommon/awkward in everyday speech. Stick to the first two for neutral style.

How do I pronounce it? Where is the stress?

Чия: stress on the last syllable — chi-YA.
це: one syllable — tse (like “ts” + “eh”).
сумка: stress on the first syllable — SÚM-ka.
Approximate: “chy-YA tse SÚM-ka.”
Sound tips: ч = “ch” in “church,” ц = “ts” as in “cats,” у = “oo” in “book.”

Can I use кого to ask “whose,” like “Кого це сумка?”?

No. Use чий/чия/чиє/чиї for “whose.”

Correct: Чия це сумка?
Incorrect: Кого це сумка?
If you want “Who has the bag?” ask with у кого:
У кого ця сумка? or У кого є ця сумка?

Can I say “that” instead of “this,” like “Whose bag is that?”

Yes:

Чия то сумка? (colloquial/neutral “that”)
Чия та сумка? (“that bag,” with attributive та)
You can also point more specifically: Чия ота сумка? (“that bag over there”)

If I don’t name the item, what form should I use?

Use the neuter to agree with це:

Чиє це? = “Whose is this?”
If you name the item and it’s feminine (like сумка), use чия: Чия це сумка?

Are there synonyms for сумка?

сумочка (diminutive: “handbag/purse”)
торба (bag/sack; common in some regions and styles)
пакет (plastic bag/shopping bag)
Choose based on the type of bag and register.

Any quick politeness tips?

Add softeners like:

Перепрошую, чия це сумка? (“Excuse me, whose bag is this?”)
Скажіть, будь ласка, чия це сумка? (“Tell me, please, whose bag is this?”)