When combined, 手 + 电 + 筒 (shǒu + diàn + tǒng) creates a clear and literal image: a “hand-held electric tube,” which is precisely what a flashlight is.
While a flashlight itself isn't a deep cultural artifact, the word 手电筒 is a fantastic window into how modern Chinese vocabulary is formed. Unlike English, which might borrow words (e.g., “torch” from French) or name things based on their function (“flashlight”), modern Chinese often builds new words by combining existing characters in a logical, descriptive way. This “Lego-like” approach makes many technical terms surprisingly transparent. Once you know 手 (hand), 电 (electric), and 筒 (tube), you can deconstruct the word and understand the concept immediately. This contrasts with the English “torch,” a word that historically refers to a flaming stick. In Chinese, there is no such ambiguity; 手电筒 is exclusively electric. This logical, compositional naming strategy is a key feature of the modern Chinese language, making it adaptable and relatively easy to learn for new inventions.
手电筒 is a common, everyday word used in neutral contexts. It is neither formal nor informal.