<p><strong>Adjective</strong></p><ul><li>Of, showing, or characterized by deep thought.</li><li>Of grave or somber disposition, character, or manner: a serious occasion; a serious man.</li><li>Synonyms: staid, sedate, sober.</li><li>Being in earnest; sincere; not trifling: His interest was serious.</li><li>Antonyms: trifling, frivolous.</li><li>Requiring thought, concentration, or application: serious reading; a serious task.</li><li>Weighty or important: a serious book; Marriage is a serious matter.</li><li>Synonyms: grave, momentous.</li><li>Antonyms: trivial.</li><li>Giving cause for apprehension; critical: The plan has one serious flaw.</li><li>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.</li></ul><p><strong>Noun</strong></p><ul><li>That which is of importance, grave, critical, or somber: You have to learn to separate the serious from the frivolous.</li></ul><p><strong>End of Response</strong></p>