Learn Hardcore Turkish: Lütfen balonu şişir.

Lütfen = please (politeness marker)
balonu = the balloon (direct object, accusative)
şişir = inflate/blow up (imperative, 2nd person singular) Turkish is typically SOV (Subject–Object–Verb), so the literal structure is: Please + the-balloon + inflate.

Why is it balonu and not just balon?

Because the balloon is definite/specific. Turkish marks definite direct objects with the accusative ending (-ı/-i/-u/-ü). balon + -u → balonu. If you mean “a balloon” (indefinite), you would say Lütfen balon şişir or more naturally Lütfen bir balon şişir.

What exactly is the verb form şişir?

It’s the 2nd-person singular imperative of şişirmek “to inflate.” Morphology: şiş (swell) → intransitive verb şişmek (to swell) → causative şişir- (to cause to swell = inflate) + zero imperative ending → şişir “inflate!” The negative imperative is şişirme “don’t inflate.”

How can I make this request more polite or formal?

Polite formal imperative (plural/formal you): Lütfen balonu şişirin.
Polite “would you…” (aorist question): Lütfen balonu şişirir misiniz?
Polite “could you…” (ability): Lütfen balonu şişirebilir misiniz? For a friend (singular you): … şişirir misin? or … şişirebilir misin?

Where can I place lütfen in the sentence?

All of these are possible, with slight differences in emphasis:

Lütfen balonu şişir. (most neutral/natural)
Balonu lütfen şişir. (emphasizes the object a bit)
Balonu şişir lütfen. (sometimes sounds a bit insistent)
Lütfen can also follow the verb alone for a softer afterthought: Şişir lütfen.

How do I pronounce this?

Lütfen: the ü is like French “u” in “tu”; say roughly “LYOOT-fen.”
balonu: “ba-LOH-noo.”
şişir: “shi-SHEER,” with ş like English “sh” and a tapped r (quick single flap).

Does şişir mean “blow up” as in “explode”?

No. şişir = “inflate/blow up (with air).” For “blow up (explode),” use patlat.

“Please don’t pop the balloon”: Lütfen balonu patlatma.

Can I replace “the balloon” with “it”? Where does the pronoun go?

Yes. o (it) in the accusative is onu. Typical placement is before the verb:

Lütfen onu şişir.
You can also say Onu lütfen şişir or, for emphasis, Şişir onu, though SOV is the default.

How do I say “Please inflate the balloons” (plural)?

Use the plural plus accusative: Lütfen balonları şişir.
If you mean an indefinite quantity: Lütfen birkaç balon şişir (“please inflate a few balloons”).

How do I say “Please don’t inflate the balloon”?

Negative imperative with -ma/-me: Lütfen balonu şişirme.
Stronger: Sakın balonu şişirme. (“Don’t you dare/under no circumstances…”)

What are some other useful forms of this verb?

Present continuous: Balonu şişiriyorum. (“I’m inflating the balloon.”)
Past: Balonu şişirdim. (“I inflated the balloon.”)
Future: Balonu şişireceğim. (“I will inflate the balloon.”)
Aorist (habitual/general): Balonu şişiririm. (“I (usually) inflate the balloon.”)

Is there a difference between şişmek and şişirmek?

Yes. şişmek is intransitive “to swell/bloat” (no direct object): Balon şişti (“The balloon swelled/filled up”).
şişirmek is transitive/causative “to make (something) swell/inflate”: Balonu şişirdim (“I inflated the balloon.”)

Why does balon take -u (not -ı/-i/-ü) in the accusative?

Because of 4-way vowel harmony. The last vowel in balon is o (back, rounded), so the accusative chooses -u.
Examples: ev-i (house-ACC), köy-ü (village-ACC), araba-yı (car-ACC; note the buffer -y because the noun ends in a vowel).

Do I need to say sen (“you”)?

No. The imperative already implies “you.” Use Sen lütfen balonu şişir only for emphasis or contrast (e.g., “You, please inflate the balloon”).

Can the object come after the verb?

Yes, but the neutral order is object–verb.

Neutral: Balonu şişir.
Emphatic/colloquial: Şişir balonu. (puts focus on the verb or adds afterthought feel)

How can I say “Let’s inflate the balloon” or add details like “with a pump” or “a little”?

Suggestion (let’s): Balonu şişirelim. or Hadi balonu şişirelim.
With a pump: Lütfen balonu pompayla şişir.
A little / more: Lütfen balonu biraz şişir. / Lütfen balonu daha fazla şişir.