In French, the term "nouvelle" is indeed commonly used to refer to both novelettes and novellas, which can be confusing. However, there are alternative terms that you can use to differentiate between the two. For a novelette, you can use the term "nouvelle courte" (short story) or "récit court" (short narrative) to emphasize its shorter length. For a novella, you can use "roman court" (short novel) or "nouvelle longue" (long story) to indicate that it is longer than a novelette, but still shorter than a full-length novel. Keep in mind that the distinction between these terms might not be as clear or widely recognized in French as it is in English.