Sentence stress is the combination of weak and strong words in a sentence, which creates a sort of rhythm. The first step in learning how sentence stress works, is to know which words are weak and which ones are strong. After that, you need to know how the stress patterns are used to make a conversation be clear and go smoothly.

One way to help a conversation be more clear, is to put strong stress on a weak word when necessary. This could happen if a weak word becomes especially important to the topic of the conversation, or if it is needed to help clarify what you are talking about. Here are some examples to illustrate.

Example 1:
He wants to leave now.
This is a basic sentence with the basic stress pattern. There are only two strong words in this sentence — the two verbs: “wants” and “leave”.

He wants to leave now.
This time, the word “he” is also stressed, but this is not the basic pattern. Therefore, this sentence implies that something was not clearly understood, and so you are indicating specifically which person wants to leave — perhaps someone thought that you wanted to leave, or perhaps someone was unsure about exactly who wanted to leave.

Example 2:
She put the box on the desk.
This is a basic sentence with the basic stress pattern. There are three strong words — the verb and the nouns: “put”, “box”, and “desk”.

She put the box on the desk.
Now the sentence has four stressed words. The word “on” is not normally strong, but here it is stressed to clarify the exact location of the box — perhaps someone else tried to find the box by the desk, or under the desk.

The overall rule is that the most important words in the sentence need to sound the strongest. A weak word should always stay weak unless you have a reason to make it strong. If you put stress on a weak word incorrectly, it can cause some confusion, or slow down the conversation. The person you are speaking to may wonder if you are both understanding each other ok, or may become a bit hesitant and stop to double check what you really mean to say.