# observable

/əbˈzɝvəbəɫ/ (US) · /ɒbzˈɜːvəbəl/ (UK)

Source: https://englishreference.com/word/observable
Updated: 2026-08-08

## Senses

### 1. able to be seen

adjective · CEFR B2

able to be seen, noticed, or measured.

For teachers: capable of being perceived or noticed; discernible through the senses or scientific instruments.

- The changes in the weather were observable even without special equipment.
- The researchers noted that the chemical reaction produced an observable change in color within seconds of the two liquids being mixed.

### 2. measurable property

noun · CEFR C1 · Technical

a physical property that a scientist can measure directly.

For teachers: a physical quantity or property that can be measured directly in an experiment.

- Temperature is an observable that helps us understand how a system changes.
- In quantum mechanics, an observable is represented by an operator that acts on the state of the physical system.

Usage: In physics, this is often used as a countable noun.

## Examples

- The moon is clearly observable tonight.
- Scientists look for observable changes in the atmosphere to predict how the weather might shift over the next few days.
- While the underlying mathematical models are abstract, the theory remains grounded in observable phenomena that can be verified through repeated experimentation in a controlled laboratory setting.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.