This is probably the most frequently-asked-question we get.
To answer it, all we can say is this: Different species of trees look different at different times of year and at different stages of their growth. Some homeowners watch their trees so carefully that they can often tell if something weird is going on. However, it usually takes a trained and experienced pair of eyes to see what's unusual or "not quite right" about a particular tree.
When you call for a tree inspection, rely on an arborist who has the experience, knowledge, and qualifications to do a thorough and accurate assessment.