Learn Hardcore Turkish: Toplantıdayken telefonumu sessize alıyorum. - While I am in the meeting, I put my phone on silent.

toplantı = meeting
-da = locative case (at/in), choosing -da rather than -de by vowel harmony
-yken = while (the buffer y is used because the preceding part ends with a vowel)

So: toplantı + da + yken → Toplantıdayken = while at the meeting.

Why is it Toplantıdayken and not Toplantıyken?

Because -yken after a noun typically attaches to a case-marked form to mean while in/at/as. You want while at the meeting, so you add the locative -da first:

Toplantıdayken = while at the meeting
Toplantıyken would suggest while (it is) a meeting, which is not idiomatic here.

Compare: Evdeyken (while at home), not Evyken.

How is -yken different from -ınca/-ince?

-yken = while, during (simultaneous actions or states). Example meaning: While I’m in a meeting, I silence my phone.
-ınca/-ince = when/once/as soon as (a triggering moment). Example: Toplantı başlayınca telefonumu sessize alırım = When the meeting starts, I put my phone on silent.

Use -yken for overlap in time; use -ınca/-ince for when X happens, then Y.

Why is telefonumu in the accusative?

Because it’s a specific, definite direct object: my phone. In Turkish, specific objects take the accusative -(y)ı/-(y)i/-(y)u/-(y)ü. Since the object is possessed (my), it’s inherently specific, so you mark it accusative: telefonum (my phone) → telefonumu (my phone, as object).

How exactly is telefonumu formed?

Step by step:

telefon = phone
- -(I)m (1st person possessive) → telefonum (my phone). The vowel becomes u by 4-way harmony because the last vowel in telefon is o.
- -(y)I (accusative) → telefonumu. The last vowel before the case is u, so you add -u; no buffer y is needed because the word ends in a consonant.

Is the final -mu the question particle?

No. In telefonumu, -mu belongs to the possessive+accusative endings, not the question particle. The yes–no question particle is written separately and harmonizes: mi/ mı/ mu/ mü. For example: Telefonu mu sessize alıyorsun? (Are you silencing the phone?) Here mu is a separate word.

What does sessize almak literally mean, and why the -e?

Sessize almak literally means to take (something) to silent, i.e., to put it on silent. The -e is the dative (to/toward) used with adjectives/nouns to express changing something into a state:

sessiz (silent) → sessiz-e (to silent [mode/state]) Similar patterns:
Uçak moduna almak (to put into airplane mode)
Sessize çevirmek also exists but sessize almak is the most common for phones.

Why not sessizce?

Sessizce means quietly (adverb), describing how an action is done. Here you’re not doing something quietly; you’re changing the phone’s state to silent. That’s why you need sessize (to silent), not sessizce.

Why is it alıyorum instead of alırım?

Both are possible, with a nuance:

Alıyorum (present continuous) can describe current, ongoing action or a repeated habit in conversational style.
Alırım (aorist) is the default for habits and routines. So for a general habit, many speakers prefer Toplantıdayken telefonumu sessize alırım, but alıyorum is also common and natural in everyday speech.

Can I omit the subject pronoun ben?

Yes. Turkish verb endings show the subject. Alıyorum already marks 1st person singular, so Ben is unnecessary unless you want emphasis. You could say Ben toplantıdayken telefonumu sessize alırım to stress I.

Can the word order change?

Yes. Adverbials and objects are flexible, but the verb typically comes last. Some natural variants:

Toplantıdayken telefonumu sessize alıyorum (neutral)
Telefonumu toplantıdayken sessize alıyorum (slight focus on my phone)
Toplantıdayken sessize alıyorum telefonumu (more marked; stylistic/emphatic)

Keep the verb final for the most neutral tone.

Could I say Toplantıda instead of Toplantıdayken?

You can: Toplantıda telefonumu sessize alıyorum is grammatical and often fine. -dayken emphasizes simultaneity (while I’m at/in the meeting). Toplantıda is looser (at the meeting) and may sound more like location; meaning is usually understood the same in this context.

Why is it -da (Toplantıda-) and not -de or -ta?

Locative case alternates by harmony and voicing:

-da/-de by vowel harmony (a/ı/o/u → -da; e/i/ö/ü → -de)
It also has -ta/-te after voiceless consonants Since toplantı ends with a vowel and has back vowels, you choose -da, yielding toplantıda. No devoicing to -ta is needed because the preceding sound is a vowel.

How do I generalize to during meetings (plural)?

Use the plural and optionally keep -yken:

Toplantılarda telefonumu sessize alırım = I silence my phone at meetings.
Toplantılardayken telefonumu sessize alırım = While I’m at meetings, I silence my phone. Both are natural; the -yken version highlights simultaneity a bit more.

Are there synonyms for sessize almak or related expressions?

Telefonumu sessize almak = put my phone on silent (most common)
Telefonu susturmak = silence the phone (also used)
Telefonun sesini kısmak = turn the volume down
Telefonu kapatmak = turn the phone off (different action)