ACF

ACF is an initialism that can refer to several concepts across different disciplines. Among the most common usages are the Autocorrelation Function in time-series analysis and the WordPress plugin Advanced Custom Fields.

The Autocorrelation Function, or ACF, measures the correlation between a time series and a lagged version of itself. For a stationary process, the autocorrelation at lag k describes how observations separated by k time units relate to each other. The ACF helps identify repeating patterns, seasonality, and the persistence of effects. In practice, the sample ACF is estimated from data and is used in model selection and diagnostic checks, with significant spikes at certain lags suggesting structure to model.

Advanced Custom Fields is a WordPress plugin that enables adding custom fields to posts, pages, and custom post types. Field types include text, image, select, checkbox, date picker, repeater, and flexible content. The Pro version adds additional field types and features such as gallery fields, options pages, and local JSON for version control. ACF integrates with the WordPress admin interface and uses PHP code to render fields and save data, allowing developers to create bespoke content schemas tailored to their site’s needs.

Other uses exist; for example, in various domains ACF can denote organizations, projects, or technical terms. Context usually clarifies which meaning is intended.