Sigmoid curve
- Pronunciation
- /SIG-moyd KURV/
- Category
- General Biology
- Singular
- sigmoid curve
- Plural
- sigmoid curves
Definition
An S-shaped curve produced by a sigmoid function, characterized by slow initial change, a steep middle phase, and asymptotic approach to a maximum. In , sigmoid curves commonly model phenomena with lower and upper limits, such as growth, kinetics, or dose-response relationships.
Etymology
From Greek sigma (Σ), the letter whose shape the curve resembles, + -oid (resembling)
Example
The cumulative of mosquitoes from a cohort of often follows a sigmoid curve: few individuals emerge at low temperatures, emergence accelerates through an optimal thermal range, then plateaus as physiological limits are reached.
Synonyms
- S-curve
- sigmoid function curve
Related Terms
- logistic growth
- Carrying capacity
- dose-response curve
- enzyme kinetics
- Population dynamics
- thermal accumulation model
Usage Notes
Distinguished from simple by its upper asymptote. In entomology, sigmoid curves fit thermal performance curves, models, and mortality-survival data. The inflection point marks the maximum rate of change and often corresponds to biologically meaningful thresholds such as LD50 or optimal temperature.