of grave or somber disposition, character, or manner: a serious occasion; a serious man.
being in earnest; sincere; not trifling: His interest was serious.
requiring thought, concentration, or application: serious reading; a serious task.
weighty or important: a serious book; Marriage is a serious matter.
giving cause for apprehension; critical: The plan has one serious flaw.
Medicine/Medical. (of a patient's condition) having unstable or otherwise abnormal vital signs and other unfavorable indicators, as loss of appetite and poor mobility: patient is acutely ill.
noun
that which is of importance, grave, critical, or somber: You have to learn to separate the serious from the frivolous.
Origin of serious
1400–50;late Middle English < Latinsērius or Late Latinsēriōsus; see -ous, -ose1
mid-15c., "expressing earnest purpose or thought" (of persons), from Middle French sérieux "grave, earnest" (14c.), from Late Latin seriosus, from Latin serius "weighty, important, grave," probably from a PIE root *swer- (4) "heavy" (cf. Lithuanian sveriu "to weigh, lift," svarus "heavy;" Old English swære "heavy," German schwer "heavy," Gothic swers "honored, esteemed," literally "weighty"). As opposite of jesting, from 1712; as opposite of light (of music, theater, etc.), from 1762. Meaning "attended with danger" is from 1800.
