Onun itirazı mantıklı değil.

His objection is not reasonable.

Breakdown of Onun itirazı mantıklı değil.

• onun: his
• itiraz: the objection
• mantıklı: reasonable

Questions & Answers about Onun itirazı mantıklı değil.

What does onun mean and why is it used here?

onun is the third person singular possessive pronoun in Turkish, meaning “his” or “her.” It goes before a noun to show that something belongs to that person. In “Onun itirazı mantıklı değil,” onun tells us whose objection we’re talking about: “His/Her objection…”

In itirazı, is the -ı an accusative ending or a possessive suffix?

It’s the third person singular possessive suffix, not the accusative. When you use a possessive pronoun like onun, the noun takes a matching possessive ending. So itiraz + ı = “his/her objection.” It just happens to look like the accusative -ı, but here it marks possession.

Why is the adjective mantıklı formed with -lı? How does vowel harmony work?

Turkish adds the adjectival suffix -lı/-li/-lu/-lü to roots to mean “having X” or “full of X.” Vowel harmony makes the suffix match the last vowel of the root:

• In mantık, the last vowel is ı (back, unrounded).
• So -lı stays back/unrounded: mantık + lı = mantıklı (“logical”).

What role does değil play in this sentence?

değil is the negative copula in Turkish (“is not”). In affirmative adjective sentences you often drop any form of “to be” (O güzel = “It/That is beautiful”), but to express negation you use değil after the adjective:
“mantıklı değil” = “is not logical.”

Could we just say mantıksız instead of mantıklı değil?

Yes. Turkish offers two ways to negate adjectives:
1) The suffix -sız/-siz/-suz/-süz (with vowel harmony), e.g. mantık + sız = mantıksız (“illogical”).
2) The adjective + değil, e.g. mantıklı değil (“is not logical”).
Both mean the same here, though mantıklı değil often sounds slightly softer or more neutral.

Why is the word order Onun itirazı mantıklı değil and not the other way around?

The basic Turkish order for nominal sentences is Subject + Predicate.

• Subject: Onun itirazı
• Predicate: mantıklı değil
  You can shift words for emphasis or style, but the neutral pattern is subject first, then the predicate (adjective + değil).

Can we drop onun and just say İtirazı mantıklı değil?

Technically the possessive suffix -ı already implies “his/her,” but native speakers include onun for clarity. Without onun, itirazı still looks possessed, and people will wonder “Whose objection?” So it’s best to keep onun.

How would you say “Their objections are not logical” in Turkish?

Use the plural possessive pronoun onların, the plural suffix -lar, and the third-person plural possessive ending -ı on itiraz:
Onların itirazları mantıklı değil.

How do I say “Your objection is not logical”?

Replace onun with senin for “your” and adjust the possessive suffix accordingly:
Senin itirazın mantıklı değil.