According to an example, a method for data trend analysis may include retrieving data from data sources, associating the data with a time, and identifying co-occurrences of terms and concepts within the data. In response to determining that co-occurrences of term and concept pairs reach a predefined threshold, the method may include adding the term and concept pairs to an ontology. The method may include logging occurrences of terms in the ontology within the data with respect to associated data times, identifying a plurality of time periods, and for one of the plurality of time periods and for the logged terms, determining a first score indicative of a weighted term frequency metric for a logged term within the data during the one time period, and determining a second score indicative of a commonality of a presence of the logged term within the data among the plurality of time periods.