What is the difference between chiggers & ticks?

Mite vs. arachnid. Ticks are arachnids (in the same class as spiders and scorpions) and small but visible to the naked eye. Chiggers are mites and too small to be seen. Tick bites usually occur with one tick while chiggers occur in bunches. Ticks spread dangerous diseases such as lyme disease and rocky mountain spotted fever. Chigger bites are very itchy and annoying but don't spread dangerous illnesses.
Different species. Chiggers and ticks are different species of insects, though both can bite.