Hi Herbert, Yes, the explanation about the second sentence not lacking anything isn't very good. The real reason the second sentence is "where" is because the object is a location (the place where "my mother works"). Here's the rule for these relative terms: Applicable to location = use "where" (e.g. "The theater where Mike works is...") Applicable to a person/people = use "who/whom" (e.g. "The person who told me was...") Applicable to a specific time = use "when" (e.g. "Friday was the day when he informed me...") Applicable to a procedure = use "how" (e.g. "Mixing the ingredients was how the chef created...") Applicable to a reason = use "why" (e.g. "Her being obnoxious was why her friend decided to...") Applicable to none of these = use "that/which" I hope I've helped. Please let me know if you have any more questions.

I think you probably answered part of your own question by saying "the second sentence doesn't lack anything". Logically, "doesn't lack anything" must mean "has something" (i.e. has a subject). In the television example, "the time spent with television personalities". I think time itself is a subject, but it is not a physical location, so using "where" is not correct. In the theatre example, the "subject" is a physical location (i.e. the theatre), where she worked. So using "where" is correct. However, English is such a fuzzy language, exceptions exist and they may not be "proper grammar". For example, "In the time where people and machines come together...". It should be "In the time when ....". But in normal speech you can hear this sometimes, and no one seems to bother about correcting it.