Observation
An observation is information gathered directly through the senses or with instruments, recorded exactly as it happens without interpretation.
Definition
An observation is something you notice with your senses or with a tool: what you see, hear, smell, or feel, or what you read off a thermometer or ruler. Observations can be qualitative (a description) or quantitative (a number with a unit), and they are the raw material of science on which questions, hypotheses, and inferences are built. A rigorous observation is stated without interpretation and specifies its conditions (time, temperature, instrument, resolution) so another investigator can judge its reliability. Instruments extend observation far beyond human senses, but they add their own uncertainty, which must be recorded alongside the value.
Example
Watching salt dissolve, a student writes: "The water looks cloudy at first, then turns clear; it took about 30 seconds with stirring." Observing a cart on a ramp: "The cart took $1.8\ \text{s}$ to reach the bottom of the $1.5\ \text{m}$ ramp, the wheels rattled, and it stopped $0.6\ \text{m}$ past the end." A careful plant-growth entry reads: "Day 10, 08:15, seedling B3, height $47\ \text{mm}$ from soil surface to apical tip, metric ruler with $1\ \text{mm}$ divisions, uncertainty $\pm 0.5\ \text{mm}$; two lowest leaves yellowing at the margins."
Key Insight
Write down what you actually see, not what you think it means: "the plant is wilted" is an observation, "the plant is thirsty" is a guess. Good observations are specific enough that another student could picture exactly what happened. Observation is never perfectly neutral, since what you choose to measure reflects what you expect to matter, and recording conditions and instrument limits is how scientists keep that bias visible and correctable.