1. The Core Idea

IS is a form of the verb to be
[IS ist eine Form des Verbs „sein“]

DO is an auxiliary (helper) verb used with other verbs
[DO ist ein Hilfsverb, das mit anderen Verben verwendet wird]

👉 The key question:
Is there a real action verb — or only “be”?
[Gibt es ein Tätigkeitsverb – oder nur „sein“?]

2. When to Use IS

Use IS when the main verb is “to be”

[Verwende IS, wenn das Hauptverb „sein“ ist]

This includes:

• identity [Identität]
• condition – it’s cold [Zustand]
• age – I am old [Alter]
• job – I am a teacher [Beruf]
• location – I am at home [Ort]
• feelings – How are you? [Gefühle]
• description – The dog is big [Beschreibung]

Examples

He is tired → Is he tired?
[Er ist müde → Ist er müde?]

The shop is open → Is the shop open?
[Der Laden ist offen → Ist der Laden offen?]

Rule:
If the sentence already has is / are / was / were, do NOT use DO.
[Wenn der Satz „sein“ enthält, wird DO nicht verwendet]

3. When to Use DO / DOES

Use DO / DOES with normal verbs

Examples of normal verbs:
work, live, like, eat, play

[Verwende DO / DOES bei normalen Verben]

Examples

You live here → Do you live here?
[Du wohnst hier → Wohnst du hier?]

She works here → Does she work here?
[Sie arbeitet hier → Arbeitet sie hier?]

Rule:
If the verb is NOT “be”, you need DO / DOES for questions.
[Wenn das Verb nicht „sein“ ist, brauchst du DO / DOES]

4. Simple Comparison

BE vs Normal Verb

She is tired → Is she tired?
She works here → Does she work here?

❌ Is she work here?
✅ Does she work here?

[❌ Ist sie arbeitet hier? → falsch]
[✅ Arbeitet sie hier? → richtig]

5. Quick Test

Ask yourself:

👉 Can I answer with a noun or adjective?
→ use IS
[Kann ich mit Adjektiv/Substantiv antworten? → IS]

👉 Do I need an action verb?
→ use DO / DOES
[Brauche ich ein Tätigkeitsverb? → DO / DOES]

6. CAN – Questions

Use CAN for:

• ability [Fähigkeit]
• permission [Erlaubnis]
• requests [Bitte]
• possibility [Möglichkeit]

Structure

CAN + subject + base verb
[CAN + Subjekt + Grundform]

Can you swim?
Can she help?

❌ Can she swims?
✅ Can she swim?

Important:
CAN replaces DO in questions.
[CAN ersetzt DO]

7. One Rule to Remember

If the verb is be → use IS / ARE
[Wenn „sein“ → IS / ARE]

If the verb is anything else → use DO / DOES
[Wenn anderes Verb → DO / DOES]

If you ask about ability or permission → use CAN
[Bei Fähigkeit/Erlaubnis → CAN]

8. The Most Important Rule

👉 If there is no “is / are / was / were”, you usually need do / does / did.

[Wenn kein „sein“-Verb da ist, brauchst du meistens DO / DOES / DID]