This bachelor thesis focuses on the development, structure, and influence of Swedish Sign Language (Svenskt Teckenspråk, STS). STS has a rich history dating back to the 18th century, with significant contributions from individuals like Per Aron Borg, who founded the first school for the deaf in Sweden in 1808. Sign formation involves manual components (hand shapes, locations, movements) and oral components (mouth movements), creating a rich vocabulary. Grammatical categories in STS include nouns, verbs, adjectives, and pronouns. The thesis examines sign formation processes, including motivated forms and numeral incorporation. STS has influenced other sign languages, contributing to Finnish Sign Language through Carl Oscar Malm's work and Portuguese Sign Language through Per Aron Borg's efforts in Lisbon. Swedish missionaries introduced STS to Eritrea in the mid-20th century. Also presented are social aspects that briefly describe the situation and opportunities that sign language users have in different circumstances.