Absences refer to missing part or whole days of work due to personal illness, personal business, or other reasons. May be avoidable and unavoidable. (Thompson)
“Absenteeism is failing to report for scheduled work. As such, it is the violation of a social obligation to be in a particular place at a particular time. Traditionally, absenteeism was viewed as an indicator of poor individual performance and a breach of an implicit contract between employee and employer. Thus, it was seen as a management problem and framed in economic or quasi-economic terms. Indeed, economists most frequently view absenteeism in labor supply terms. More recently, absenteeism has increasingly been viewed as an indicator of psychological, medical, or social adjustment to work.” (Johns, 2007)
“Employee absences due to personal illness, personal business and absence without leave, as measured in number of hours. (Goff, Mount, & Jamison, 1990)

As defined by Cynthia Thompson. Johns, G. (2007). Absenteeism. In  G. Ritzer (Ed.), Blackwell encyclopedia of sociology. Blackwell Publishing. Blackwell Reference Online. Retrieved June 13, 2007, from Absenteeism. (2002). In F. Abate, (Ed.), The Oxford American dictionary of current English in English dictionaries and thesauruses. UK: Oxford University Press, Inc. Internet Explorer. (16 June 2003). Goff, S. J., Mount, M. K., & Jamison, R. L. (1990). Employer supported childcare, work/family conflict, and absenteeism: A field study. Personnel Psychology, 43, 793-809.