I often see a single word being used when it should be two words. Here are some examples.
Logon and log on
“Logon” is a noun, describing the procedure used to get access to an operating system. “Logon” can also be used as an adjective, as in the “logon procedure.”
“Log on” is a verb. “I need to log on to my computer.”
The same distinctions apply to “login” and “log in.”
Alot and a lot
“Alot” is not a word. Fortunately, Word’s spell checker flags this common error.
“A lot” means many. “A lot of people think that way.”
Everyday and every day
“Everyday” is an adjective meaning ordinary or typical. “The store offers everyday values.”
“Every day” is an adverb referring to something that occurs each day. “The store offers values every day.”
Backup and back up
“Backup” is a noun, often referring to computer files that have been saved elsewhere. “My backup was corrupted.” “Backup” can also be an adjective. “It’s important to have a backup plan.”
“Back up” is a verb, referring to the action of moving backwards (e.g., a car) or of saving an electronic file to another location. “I am going to back up my computer now.”
Follow-up and follow up
“Follow-up” can be used as a noun, meaning something that follows. For example, “the follow-up was effective.” “Follow-up” can also be used as an adjective. “Follow-up actions are essential.”
“Follow up” is a verb, indicating action. “I will follow up with you tomorrow.”
“Followup” is not a word.