English Vocabulary Flash Cards @ englishpdf.com and englishteststore.com File 164 diligence (n) Careful and persevering effort to accomplish what is undertaken dilute (v) To make more fluid or less concentrated by admixture with something diminution (n) Reduction dimly (adv) Obscurely diphthong (n) The sound produced by combining two vowels in to a single syllable or running together the sounds diplomacy (n) Tact, shrewdness, or skill in conducting any kind of negotiations or in social matters diplomat (n) A representative of one sovereign state at the capital or court of another diplomatic (adj) Characterized by special tact in negotiations