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rallentando vs. ritardando

[rah-luhn-tahn-doh, rahl-len-tahn-daw] / ˌrɑ lənˈtɑn doʊ, ˌrɑl lɛnˈtɑn dɔ /

adjective

  1. slackening; becoming slower (used as a musical direction).

[ree-tahr-dahn-doh, ree-tahr-dahn-daw] / ˌri tɑrˈdɑn doʊ, ˌri tɑrˈdɑn dɔ /

adjective

Music.
  1. becoming gradually slower.