Learn Hardcore Turkish: Arkadaşım bugün mesafeli.

In Turkish, the present tense “to be” in third person is usually zero (nothing is added). So Arkadaşım bugün mesafeli literally maps to “My friend today distant,” which is how Turkish forms “My friend is distant today.” You only add something when you negate (değil) or ask a yes/no question (mi/mı/mu/mü), or when you use tenses like past or future.

Does the ending -ım in arkadaşım mean “I am”?

No. Here -ım is the 1st‑person possessive suffix meaning “my”: arkadaş (friend) + -ım → arkadaşım = “my friend.” The “I am” copula also looks like -(y)im/-(y)ım/-(y)um/-(y)üm, but it attaches to the predicate, not the subject (e.g., yorgunum = “I’m tired”). In your sentence, the predicate is mesafeli, not arkadaşım.

Can I change the word order? For example, say “Bugün arkadaşım mesafeli”?

Yes. Both are correct:

Arkadaşım bugün mesafeli (neutral S–time–predicate)
Bugün arkadaşım mesafeli (puts “today” up front for emphasis) Turkish typically places the main predicate at the end, but elements like time adverbs can move for emphasis without changing the core meaning.

What exactly does mesafeli mean? Is it physical distance?

Mesafeli usually describes demeanor: reserved, keeping an emotional or social distance, somewhat aloof or formal. For physical distance, Turkish more often uses uzak (“far”) or uzakta (“far away”). Compare:

Emotional: Bugün arkadaşım mesafeli.
Physical: Arkadaşım uzakta. (“My friend is far away.”) Related words:
soğuk = cold, unfriendly (stronger, negative)
resmi = formal (neutral/professional)

How do I negate this sentence?

Use değil to negate adjectives and nouns:

Arkadaşım bugün mesafeli değil. = “My friend is not distant today.” Optionally add emphasis: hiç de, pek, çok da:
Arkadaşım bugün hiç de mesafeli değil.

How do I turn it into a yes/no question?

Use the question particle mi/mı/mu/mü after the predicate, obeying vowel harmony. Since the predicate is mesafeli (last vowel i), use mi:

Arkadaşım bugün mesafeli mi? You can front the time word too:
Bugün arkadaşım mesafeli mi?

Is bugün one word or two? I’ve seen “bu gün.”

It’s one word: bugün (“today”). The spaced form bu gün is nonstandard in modern usage.

Can I add degree words like “a bit” or “very”?

Yes. Common intensifiers go before the adjective:

biraz (a bit): Arkadaşım bugün biraz mesafeli.
çok (very): Arkadaşım bugün çok mesafeli.
oldukça / epey / bayağı (quite/fairly): Bugün oldukça mesafeli.

What if the subject is plural: “My friends are distant today”?

Use plural on the subject; the predicate adjective usually stays singular:

Arkadaşlarım bugün mesafeli. Adding plural on an adjective predicate (mesafeliler) is possible but changes nuance (group/class emphasis) and is less common in neutral descriptions:
Arkadaşlarım bugün mesafeliler. (sounds like “they’re the distant ones today”)

Should I add -dir (as in mesafelidir)?

Generally no for a temporary state like “today.” -Dir is used for general truths, definitions, assumptions, or a formal tone:

Arkadaşım mesafelidir. suggests a habitual/character trait (“My friend is (generally) distant.”), not just today.

Do I need to say Benim arkadaşım or is Arkadaşım enough?

Arkadaşım already means “my friend.” You add benim for emphasis or contrast:

Benim arkadaşım bugün mesafeli, seninki değil. (“My friend is distant today; yours isn’t.”)

Any pronunciation tips for this sentence?

Arkadaşım: the final ı is the dotless i [ɯ], like the vowel in Turkish “kız”; ş is “sh.”
bugün: ü is a front rounded vowel [y], like French “u” or German “ü.”
mesafeli: stress typically near the end; the -li is “lee.”

Is there a more “dynamic” way to say this, like “is acting distant”?

Yes, use davranmak in the progressive:

Bugün arkadaşım mesafeli davranıyor. = “My friend is behaving in a distant way today.” You can also say: Bugün benden uzak duruyor. (“is keeping away from me”)

How do I say it in the past or future?

Past: attach the past copula to the adjective: Arkadaşım dün mesafeliydi. (“was distant yesterday”)
Reported past: mesafeliymiş (“apparently/it seems s/he was distant”)
Conditional: mesafeliyse (“if s/he is distant”)
Future (use “become/be” with olmak): Yarın mesafeli olacak. (“will be distant tomorrow”)

Does arkadaşım specify gender? How do I be explicit?

Turkish nouns aren’t gendered, so arkadaşım is gender‑neutral (“my friend”). To be explicit:

erkek arkadaşım often means “my boyfriend;”
kız arkadaşım often means “my girlfriend.” If you just need to clarify gender without implying a relationship, use context or phrases like erkek bir arkadaşım / kadın bir arkadaşım.