Traumatic ulcer: This is often the most common cause of a spot on the tongue, resulting from accidental bites or irritation from sharp teeth or dental work. The history of recent trauma and the appearance of the lesion can help confirm this diagnosis.

Oral candidiasis (thrush): This fungal infection can cause white spots on the tongue and other parts of the mouth. It's more common in immunocompromised individuals, those wearing dentures, or after antibiotic use.
Leukoplakia: A condition where thick, white patches or lesions develop on the tongue or the inside of the mouth. It can be associated with chronic irritation and has a potential for malignant transformation.
Fordyce spots: Small, yellowish or white bumps on the tongue that represent ectopic sebaceous glands. They are benign and often discovered incidentally.

Squamous cell carcinoma: Although less common, any persistent or changing lesion on the tongue should raise concern for oral cancer, especially in smokers or those with a history of tobacco use. Early detection is crucial for treatment outcomes.
Lichen planus: An autoimmune condition that can affect the mucous membranes inside the mouth, leading to white, lacy patches or red, inflamed tissues. It can sometimes be a precursor to more serious conditions.
Syphilis (secondary): Oral lesions, including spots on the tongue, can be a manifestation of secondary syphilis. Given the potential for serious complications if left untreated, it's a diagnosis not to be missed.

Geographic tongue: A benign condition characterized by areas of depapillation on the tongue surface, giving it a "geographic" appearance. It can sometimes be mistaken for other conditions.
Hairy leukoplakia: Associated with Epstein-Barr virus, this condition causes white patches on the tongue, typically in immunocompromised patients, such as those with HIV/AIDS.
Oral melanotic macule: A benign pigmented lesion that can appear as a spot on the tongue. It's essential to differentiate it from more serious pigmented lesions like melanoma.