The grammar book says when the verb "to be" is used in a sentence saying when or where about the subject it is a state of being verb as opposed to a linking verb.
Yes, it's confusing, but I get it, and I'll explain it to you.
The book you're using divides the verb "To Be" into two categories:
(i)
Linking Verb
"To Be" is called a linking verb when it is followed by a subject complement:
- Max is a girl. <predicate noun>
- Max is tall. <predicate adjective>
Subject complements are of two types: nouns and adjectives. Notice that prepositions and adverbs, words that introduce phrases that answer the questions "Where?" and "When?", do not fit into the above category. So, ...
(ii)
State-of-Being Verb
"To Be" is called a state-of-being verb when it is followed by a preposition or an adverb:
- Max is in the house. / Where is Max?
- grammatical form: prepositional phrase
- grammatical function: adverb
- Max's party is today. / When is the party?
- grammatical form: adverb
- grammatical function: adverb
The prepositional phrase "in the house" doesn't describe "Max", as does "tall" in "Max is tall", nor does it rename "Max", as does "a girl" in "Max is a girl." The prepositional phrase "in the house" tells us where Max is located, and the reason your book defines "To Be" as a state-of-being verb in those kinds of sentences.
The adverb "today" doesn't describe "Max's party", nor does it rename "Max's party". It answers the question "When?", and the reason your book defines "To Be" as a state-of-being verb in those kinds of sentences.
In short, and according to what you have told us about your book, here's the skinny (the simplest way of saying it):
- if "To Be" is followed by a noun or an adjective, it is called a linking verb
- Linking Verb: "To Be" + Noun or Adjective
- N & A rename or describe the subject
- Max is a girl.
- Max is tall.
- if "To Be" is followed by a preposition or an adverb, it is called a state-of-being verb
- State-of-Being Verb: "To Be" + Preposition or Adverb
- P and A describe the subject in time and space
- Max is in the house.
- Max's party is today.