What is there, and where is it?
You are looking for a teacher and checking what is in a classroom. You already know あります from lesson 26 and で for the place of an action from lesson 32. Here you connect that knowledge with a new distinction: objects, people and animals. Get familiar with the word meanings before building sentences.
A book, a cat or a tree
Use あります to say that an object is present. Use います for a person or an animal. English may say that something is lying or standing somewhere; in these Japanese patterns, first choose according to what is present. You can locate a book on a table without a separate verb for ‘lying’.
Notice the tree: a plant is alive, but this pattern uses あります for it. Use ‘people and animals’ as your cue for います. Look at the word before が first, then choose the verb. The location does not determine that choice.
The negative forms are ありません and いません. Replace the whole polite form; do not add です after あります or います. This lesson practises these polite forms directly. You do not need to form dictionary forms yet.
本があります。
ねこがいます。
木があります。
先生がいません。
Adding a place
To say what is present in a place, build: placeに + object or personが + あります or います. Here に marks the place of presence. が introduces what or who you find there. Read the sentence as three blocks first instead of assigning each particle one fixed English word.
A place can contain several words. 机の上 means ‘the top of the desk’ and, in these sentences, ‘on the desk’. 机の下 means ‘under the desk’. の connects the desk to the relative position; に follows the whole place block. This gives 机の上に.
Keep the location and change only what is present. The book takes あります, the cat います. This separates the choice belonging to the place block from the one belonging to the object or animal.
机の上に本があります。
机の下に本があります。
机の下にねこがいます。
机の下に本がありません。
What is there, or where is it?
Choose what you want to find out first. 教室に何がありますか asks which objects are in the classroom. 教室にだれがいますか asks which person is there. To ask about animals, use 何 with います, for example when you know an animal is present but do not yet know which one.
To locate a known object or person, make it the topic: 本はどこにありますか or 先生はどこにいますか. どこ is the unknown place. You are now asking where the book or teacher is, rather than what is in a classroom. は and が serve different purposes here; do not swap them at random.
An answer need not repeat information that is already clear. 教室にいます can answer where the teacher is. A yes/no question about a cat can be answered with はい、います or いいえ、いません. The short answer keeps the verb choice from the question.
教室にだれがいますか。
先生はどこにいますか。
教室にいます。
Being there or doing something
The library can be where the teacher is present or where the teacher studies. With います you locate a person, using に here. With 勉強します you describe an action, and で marks where it takes place. The same place word can therefore take a different particle when the message changes.
If you are unsure, check the sentence ending: is the main message presence or an action such as studying? Then choose the place marker. This lesson practises the presence of objects, people and animals; it does not state a rule for every possible sentence with あります. Events are outside this lesson.