Introduction
The safest Indonesian equivalent for omission to act is ketiadaan tindakan, because it is the only common candidate that adds nothing to the source concept. That conclusion is less obvious than it sounds.

Ask a group of English–Indonesian legal translators to render omission to act, and you are likely to hear four answers: kelalaian bertindak, keengganan bertindak, kegagalan bertindak, and ketiadaan tindakan. All four sound natural in Indonesian. They do not, however, say the same thing.

This article tests each candidate against two benchmarks: what the English term means linguistically, and how it operates within the American common law doctrine of the duty to act. It then shows, through a contract clause, how the wrong choice can change the legal effect of a translation.

The discussion is written for fellow translators, editors, and reviewers who handle common law texts into Indonesian, whether translating from scratch or post-editing machine output.

What the Source Term Actually Says
Omission denotes the non-occurrence of an act, nothing more. Black's Law Dictionary defines it, among other senses, as "the state of having been left out or of not having been done" and as something "left undone, or otherwise neglected" (Garner 2014:1260).

The word neglected in that second sense should not mislead us. It carries its everyday meaning of "left unattended," not the legal standard of negligence, which Black's treats under a separate entry. The dictionary's own illustration even describes omissions that were unintentional.

Cornell's Legal Information Institute (LII) offers a narrower definition: a failure to act where there is a responsibility to act (LII n.d.-a). In its entry on actus reus, it likewise treats omission as a failure to act (LII n.d.-b).

Two points follow for the translator:
• Omission says nothing about state of mind. It does not tell us whether the person was unwilling, forgetful, afraid, or convinced that no duty existed.

• Omission says nothing about fault. Whether the absence of action was wrongful is a separate question that the law, not the word, must answer.

Where the Law Comes In: The Duty to Act
In common law, an omission becomes legally significant only when the person had a legal duty to act. Criminal liability normally rests on a positive act; the Model Penal Code allows an omission to suffice only where the offense expressly says so or where the law otherwise imposes a duty to perform the omitted act (American Law Institute 1985, § 2.01(3)).

Traditional common law also recognizes no general duty to rescue. Under the Restatement (Second) of Torts, realizing that one's help is needed does not, by itself, create a duty to give it (American Law Institute 1965, § 314). The distinction is often framed as misfeasance (doing harm) versus nonfeasance (failing to confer a benefit).

In Jones v. United States, 308 F.2d 307 (D.C. Cir. 1962), the court listed four sources of such a duty: a statute, a special status relationship, a contractual undertaking, and the voluntary assumption of care that isolates the victim from other help. It stressed that the duty must be legal, not merely moral.

A simple scenario shows why this matters. A trained lifeguard, on vacation at a Florida hotel, watches a guest who cannot swim fall into the pool and does nothing. The guest drowns. Change one fact: the lifeguard is now on duty at that pool.

• Off duty: absent a statute or other source of duty, he stands in the position of a bystander. His failure to act is morally troubling but not, under the baseline rule, a breach of law.

• On duty: a contractual or professional duty now exists. The same failure to act may become a breach of that duty.

The word omission describes both scenarios equally well. What changes is the legal context, not the meaning of the term. Note also that several U.S. jurisdictions, such as Vermont (Vt. Stat. Ann. tit. 12, § 519), have modified the no-duty-to-rescue rule by statute, so the scenario illustrates a doctrine, not the outcome of an actual case.

Testing the Four Candidates
A good terminological equivalent should convey what the source term says and nothing it does not say. Measured against that standard, the four candidates perform very differently.

Keengganan bertindak. Keengganan describes an attitude: reluctance or unwillingness. Rendering omission this way adds a mental state that the English term does not contain. The lifeguard may indeed have been unwilling to help, but that is a finding about his motive, not part of the word's meaning. Keengganan bertindak is the right choice for reluctance to act, not for omission to act.
Kelalaian bertindak. Kelalaian is strongly associated with negligence and, in Indonesian legal usage, with fault. An omission may form part of negligence when a duty of care exists, but the two are not the same. Choosing kelalaian turns a neutral description ("he did not act") into a legal characterization ("he was at fault for not acting") that the source text has not made.

Kegagalan bertindak. This option mirrors failure to act, the phrase the LII itself uses, and it is close. Yet kegagalan tends to imply that the act was expected or required. That makes it apt once a legal duty has been established, but less neutral where, as with the off-duty lifeguard, no duty exists.

Ketiadaan tindakan. This phrase simply states that an act did not occur. It matches Garner's "state of … not having been done," preserves the noun form of the source term, and carries no implication of reluctance, fault, or breached duty. It answers the linguistic question (was an act left undone?) and leaves the legal question (was there a duty?) to the law, exactly as omission does.
In running text, the verbal form tidak bertindak is often more natural, as in A tidak bertindak ketika B jatuh ke kolam. When the term is named as a concept, however, the nominal ketiadaan tindakan is the better fit.

Why It Matters: An Indemnity Clause
In a bilingual contract, kelalaian bertindak can quietly narrow an indemnity from "any omission" to "any negligent omission."

Consider this hypothetical clause from a service agreement between a foreign company and an Indonesian contractor:
The Contractor shall indemnify and hold harmless the Company against all losses, damages, costs, and expenses arising from any act or omission to act of the Contractor, its employees, or its subcontractors in the performance of this Agreement.

The English text covers every omission, with no requirement that the Contractor be at fault. A common rendering reads:
… yang timbul dari setiap tindakan atau kelalaian bertindak Kontraktor …

The phrase tindakan atau kelalaian is so frequent in Indonesian contracts that both translators and AI tools reproduce it almost automatically. The problem is that kelalaian is a fault concept under Indonesian civil law: Article 1366 of the Civil Code (KUHPerdata) imposes liability for loss caused by kelalaian or lack of care. A judge or arbitrator reading the Indonesian text may therefore require the Company to prove negligence, a burden that does not exist in the English version.

The discrepancy is not academic. Law No. 24 of 2009 (Article 31) requires Indonesian in agreements involving Indonesian parties, and Presidential Regulation No. 63 of 2019 (Article 26) gives priority to the language the parties agree on when versions conflict. If Indonesian prevails, the narrower reading may become the operative one.

Suppose a subcontractor fails to file a mandatory regulatory notice, and the Company suffers a Rp2 billion loss from fines and delay. Under kelalaian bertindak, the Contractor can argue that it followed its procedures and was not negligent. Under the alternative below, that argument has little footing:

… yang timbul dari setiap tindakan atau ketiadaan tindakan Kontraktor …

The other candidates create similar gaps. Keengganan bertindak would suggest the Company must show unwillingness, and kegagalan bertindak may invite a debate over whether a prior duty to act existed.

Practical Guidelines
Ketiadaan tindakan is the default terminological equivalent, but context still decides the final wording:
• The term is named as a concept ("the issue concerns an omission to act"): use ketiadaan tindakan.

• The sentence simply reports that someone did not act: tidak bertindak is often more natural.

• The text expressly concerns a breach of a legal duty: kegagalan bertindak or kegagalan memenuhi kewajiban hukum is accurate.

• The source text itself says negligence: only then is kelalaian the relevant equivalent.

A useful habit is to ask two questions in order. First, was an act left undone? That is a linguistic question, and omission answers it. Second, was there a legal duty to do it? That is a legal question, and the translation should leave it exactly as open as the source text does.

The same reasoning applies across legal systems. Indonesia belongs to the civil law tradition, but the translator is not converting American law into Indonesian law; the task is to carry a common law message into the Indonesian language. Where no exact doctrinal counterpart exists, a neutral descriptive equivalent is usually safer than an Indonesian legal term with its own doctrinal consequences, and ketiadaan tindakan serves that purpose well.

Conclusion
The lifeguard did not act. Was he reluctant? Not necessarily. Was he negligent? Not necessarily. Did he break the law? That depends on whether the law imposed a duty on him to act.

What a translator can state without adding anything to the source is that there was ketiadaan tindakan. Keeping the linguistic, factual, and legal layers apart is what allows a translation to carry the same legal effect as its source, and it is a check worth applying to every common law term that looks deceptively simple.

References
American Law Institute. 1965. Restatement (Second) of Torts. St. Paul: American Law Institute Publishers.
American Law Institute. 1985. Model Penal Code and Commentaries (Official Draft and Revised Comments). Philadelphia: American Law Institute.
Garner, Bryan A. 2014. Black's Law Dictionary. 10th ed. St. Paul: Thomson Reuters.
Legal Information Institute. n.d.-a. "Omission." Wex. Cornell Law School. https://www.law.cornell.edu/wex/omission
Legal Information Institute. n.d.-b. "Actus Reus." Wex. Cornell Law School. https://www.law.cornell.edu/wex/actus_reus
Jones v. United States, 308 F.2d 307 (D.C. Cir. 1962).
Vt. Stat. Ann. tit. 12, § 519.
Kitab Undang-Undang Hukum Perdata (Indonesian Civil Code), Article 1366.
Law No. 24 of 2009 on the National Flag, Language, Emblem, and Anthem, Article 31.
Presidential Regulation No. 63 of 2019 on the Use of the Indonesian Language, Article 26.