Structure of English verbs

1. Simple

1.1. walk

1.2. play

1.3. eat

2. Complex

2.1. underline

2.2. whitewash

3. Phrasal

3.1. look out

3.2. stand up

4. Derived

4.1. unleash

4.2. reread

4.3. replay

5. Semantic

5.1. work

5.2. stay

5.3. go

6. Service

6.1. modal

6.1.1. can

6.1.2. may

6.1.3. must

6.1.4. ought to

6.1.5. need

6.2. auxiliary

6.2.1. to be

6.2.2. to do

6.2.3. will

6.2.4. to have

6.2.5. shall