Samankaltaisuus

Samankaltaisuus refers to the quality or state of being similar, or the degree to which two or more objects, concepts, or stimuli resemble each other. It is a relative and context-dependent notion; what counts as similar depends on the dimensions considered, such as shape, color, function, or statistical properties.

In everyday language, samankaltaisuus is used when comparing items, for example two paintings with similar color schemes or two cars with similar design.

In mathematics and geometry, samankaltaisuus has a precise meaning: two planar figures are similar if there exists a similarity transformation that maps one onto the other. A similarity transformation allows translation, rotation, reflection, and uniform scaling. Similar figures have proportional corresponding side lengths and equal corresponding angles, and they differ by a scaling factor called the similarity ratio.

In statistics and data analysis, samankaltaisuus is expressed by similarity or proximity measures between objects, such as cosine similarity, Jaccard similarity, or Pearson correlation, used in clustering, information retrieval, or recommendations.

In cognitive psychology and linguistics, samankaltaisuus influences categorization, memory, and generalization: entities with greater perceived similarity are more likely to be grouped together or confused.

Etymology: from Latin similis, comparable. See also similarity transformation, metric, distance, proportionality, clustering, correlation.