English Vocabulary Flash Cards @ englishpdf.com and englishteststore.com File 012 acidify (v) To change into acid acknowledge (v) To recognize; to admit the genuineness or validity of acknowledgment (n) Recognition acme (n) The highest point, or summit acoustic (adj) Pertaining to the act or sense of hearing acquaint (v) To make familiar or conversant acquiesce (v) To comply; submit acquiescence (n) Passive consent