Disinterested and uninterested are often taught as words with completely separate meanings. That distinction is useful today, but it does not tell the whole historical story.
For clear modern writing, use disinterested to mean impartial: someone has no personal stake in the outcome and can judge fairly. Use uninterested to mean not interested: someone does not feel curious about or engaged in something.
- A disinterested adviser can help us choose between the two offers.
- Maya was uninterested in the discussion about football.
In the first example, the adviser has nothing to gain from either choice. The sentence does not suggest that the adviser is bored. In the second, Maya simply does not find the topic interesting.
The history is less tidy than this modern distinction suggests. Both words have been used for lack of interest and for impartiality. Earlier usage even included uninterested meaning impartial. The use of disinterested to mean not interested also has a long history; it is not merely a recent confusion.
However, some readers object to that last use, especially in formal writing. A sentence such as “The students were disinterested in the lecture” may therefore distract readers or leave your meaning unclear.
If you mean the students were bored or did not care about the topic, uninterested is the clearer choice. Historical overlap explains the variation, while the modern distinction helps you avoid ambiguity.