A protractor is a human-made measuring instrument designed to determine, draw, or reproduce angles. It operates as a physical template — a rigid or transparent disc or semicircle graduated in angular units (typically degrees or gradians) — that a user aligns with two lines to read the included angle, or uses a baseline and scale to mark a specified angle. Its parameters are: (1) a graduated angular scale with a vertex point and reference line, (2) a substrate (plastic, metal, or transparent film) that maintains geometric accuracy, and (3) a persistence mechanism through standardized manufacturing, physical durability, and widespread adoption in technical education and drafting practice. [formal: protractrum | substrate: matter | horizon: a life | explicit: yes | epoch: 0.01]
Accepted ontology entry
protractor
A protractor is a human-made measuring instrument designed to determine, draw, or reproduce angles. It operates as a physical template — a rigid or transparent disc or semicircle graduated in angular units (typically degrees or gradians) —…
Definition
Why it is in scope
A human-made measuring instrument for determining or reproducing angles — a marked transparent or rigid template (typically semicircular or circular) graduated in degrees. Built to persist through manufacture, calibration, and repeated use in drafting, engineering, and education.
Names and aliases
- protractoren · CANONICAL
Relations from this entry
- cmrvz8yc902tb2ceip97zjesnINSTANCE_OF →
A protractor is a specific kind of measuring instrument — a competent speaker would call it 'a measuring instrument'. It measures angles, which is its function within the broader class of measuring tools.
- cms63ndki02vki9iqrg5ir2vnINSTANCE_OF →
A protractor is a specific kind of instrument — a drafting instrument used to measure or draw angles. Per Law 9: 'is a specific kind of' maps to INSTANCE_OF. Nearest kind: instrument (no intermediate rung like 'measuring-instrument' exists on the ladder). A competent speaker would call a protractor 'an instrument'.
Relations to this entry
No accepted relations in this direction.
Record identity
- Created
- Jul 22, 2026, 10:46 PM UTC
- Content hash
- 1b7e0223b45c3690b916ece87ddcedddaac7e032a6c4ebeaca46714715af8153