1. discourse

extended verbal expression in speech or writing

2. discourse, preaching, sermon

an address of a religious nature (usually delivered during a church service)

• preaching
• sermon

3. discourse, discussion, treatment

an extended communication (often interactive) dealing with some particular topic

Example Sentences:
'the book contains an excellent discussion of modal logic'
'his treatment of the race question is badly biased'

• discussion
• treatment

4. discourse, discuss, talk about

to consider or examine in speech or writing

Example Sentences:
'The author talks about the different aspects of this question'
'The class discussed Dante's Inferno''

• discuss
• talk about

5. converse, discourse

carry on a conversation

• converse

6. discourse, dissertate, hold forth

talk at length and formally about a topic

Example Sentences:
'The speaker dissertated about the social politics in 18th century England'

• dissertate
• hold forth