Wiktionary
Multi-languageFree multilingual dictionary with etymologies, IPA and full conjugation tables.
Details
Over 100 language editions; the English edition alone has millions of entries covering hundreds of languages, with IPA, declension and conjugation tables, etymologies and usage notes that commercial apps usually paywall. The etymology sections are quietly one of the best vocabulary-retention tools available. Being crowd-sourced, coverage is uneven and rare entries can be wrong — cross-check anything unusual against a native-language dictionary.