Understanding word counts is essential not only for setting and meeting writing goals but also for aligning your work with industry standards and audience expectations. Here’s a breakdown:

Flash Fiction Word Count: Typically 100 to 1,500 words. Audience expectation: Readers expect concise, impactful narratives. Every word must count.
Short Stories Word Count: Generally 1,500 to 30,000 words. However, most short stories in literary magazines or anthologies tend to be between three thousand to seven thousand words. Audience expectation: Readers anticipate a complete narrative arc but on a smaller scale. There’s more room to explore characters, setting, and plot than in flash fiction.
Novellas Word Count: Ranges from thirty thousand to fifty thousand words. Audience expectation: A novella offers more depth than a short story but remains more concise than a full-fledged novel. Readers expect a focused narrative, often centered on a singular idea or theme.
Novels Word Count: Typically between fifty thousand to one hundred ten thousand words, but this can vary based on genre. Some complex genres like epic fantasy can exceed this range. Audience expectation: Readers expect a rich and layered narrative with multiple arcs, subplots, and character developments.
Word Counts by Genre:

Romance: 50,000 – 100,000 words
Mystery/Thriller/Crime: 70,000 – 90,000 words
Science Fiction and Fantasy: 90,000 – 120,000 words, though some epic fantasies can be much longer.
Historical: 80,000 – 100,000 words
Young Adult: 50,000 – 80,000 words
Middle Grade: 20,000 – 50,000 words
Tips:

Research Industry Standards: If you’re writing with the intent to publish traditionally, always research the standards for your specific genre and target audience. Word counts can influence agents’ and publishers’ decisions.
Use Word Counts as a Guide, Not a Rule: While it’s beneficial to be aware of these counts, don’t let them stifle your creativity. Write your story, then edit.
Sometimes, stories naturally align with these standards; other times, they might require adjustment.
Consider Digital Platforms: With the rise of ebooks and self-publishing, there’s more flexibility with word counts than in traditional publishing. If your story doesn’t fit standard molds, digital might be a route to consider.
Editing Matters: A concise, well-edited novel is often more appealing to readers and publishers than a lengthy, unedited one. Always prioritize quality over quantity.
In essence, while word counts serve as valuable guidelines, the most crucial factor is the story’s quality, coherence, and engagement level.