Learn Hardcore Indonesian: Tarif ojek pagi ini lumayan murah, jadi adik laki-laki saya senang. - The motorcycle taxi fare this morning is quite cheap, so my younger brother is happy.

Ojek is a motorcycle taxi service (you ride on the back of a motorbike).
App-based motorcycle taxis are often called ojek online or ojol (e.g., via Gojek/Grab).
It’s a very common, affordable urban transport option in Indonesia.

What’s the difference between tarif, harga, ongkos, and biaya here?

Tarif: a set fare or rate (transport, phone plans, utilities). Very natural with transport: tarif ojek.
Harga: price (most general term).
Ongkos: cost/fare of travel or services (colloquial), e.g., ongkos ojek.
Biaya: cost/fee (more formal/administrative), e.g., biaya administrasi.

Is it correct to say tarif … murah without any verb like “is”?

Yes. Indonesian often drops the copula “to be” before adjectives: Tarif … murah = “The fare is cheap.”
Adalah is usually for equating nouns; it’s odd before adjectives here. Avoid Tarif … adalah murah.

How strong is lumayan? What nuance does lumayan murah have?

Lumayan ≈ “quite/pretty/fairly,” a moderate-positive degree.
Rough scale: agak (a bit) < cukup/lumayan (quite) < sangat/amat (very) < slang banget (really).
It can also stand alone to mean “not bad”: Lumayan!

Does pagi ini mean earlier this morning or the current morning? How does it differ from tadi pagi?

Pagi ini = this morning (still “today,” neutral about whether it’s over).
Tadi pagi = earlier this morning (clearly in the past).
If you’re speaking later in the day about the morning, tadi pagi is more precise.

Can I move pagi ini to other positions?

Yes: Pagi ini, tarif ojek lumayan murah. / Tarif ojek lumayan murah pagi ini.
All are natural; choose based on what you want to emphasize. Don’t split pagi and ini.

How is jadi functioning here? Could I use sehingga, maka, or makanya?

Jadi links cause to result: “so/therefore.”
Alternatives: sehingga (thereby/so that), maka (thus; formal/literary), makanya (that’s why; colloquial).
Avoid double-marking cause: don’t say Karena tarif… jadi adik…. Use either karena (because) or jadi (so), not both.

Can jadi also mean “to become”? How is that different from menjadi?

Yes. Jadi can mean “to become” in casual speech: Dia jadi marah = “He became angry.”
Menjadi is the standard verb “to become”: Dia menjadi marah (more formal).
Your sentence uses jadi as a conjunction (“so”), not as “become.”

Is adik laki-laki saya the only way to say “my younger brother”? What about adik saya laki-laki or adikku?

Most natural: adik laki-laki saya or the clitic form adikku (my younger sibling; masculine implied by context or added explicitly).
Adik saya laki-laki literally states “my younger sibling is male”; it’s more of an identification, not the usual noun phrase for “younger brother.”
Colloquial gender markers exist (e.g., adik cowok saya), but laki-laki is standard.

Is the hyphen in laki-laki necessary? Are there synonyms?

Standard spelling is laki-laki (with hyphen). You’ll also see lelaki (one word) as a synonym for “man.”
In this kinship phrase, Indonesian prefers adik laki-laki. Malay often uses adik lelaki.

Could I use pria instead of laki-laki?

Not here. Pria means “man/male” (more formal, for adults) and doesn’t fit in kinship compounds like this.
Stick with adik laki-laki in Indonesian.

Are senang, bahagia, gembira, and puas interchangeable?

Senang: happy/pleased (most neutral for small good news like a cheap fare).
Gembira: joyful/cheerful (more exuberant).
Bahagia: deeply happy (life happiness), too strong here.
Puas: satisfied (contentment after an expectation is met). Could work depending on nuance.

Can I omit laki-laki and just say adik saya?

Is tarif … lumayan murah idiomatic, or should I use ongkos?

Both are idiomatic: tarif ojek… murah and ongkos ojek… murah are common.
Tarif sounds a bit more neutral/formal; ongkos is everyday speech.

Is the comma before jadi required?

It’s optional. Many writers place a comma before a linking word like jadi to mark the pause: …, jadi …
In long sentences, the comma helps readability.

How formal is this sentence? Any casual alternatives?

Neutral and fine in everyday conversation.
More casual variants: Tarif ojol pagi ini murah banget, jadi adik gue seneng.
Slightly more formal: Tarif ojek pagi ini cukup murah, sehingga adik laki-laki saya senang.