A language learner observes that changing the initial sound in the word 'pat' to a different sound can create the words 'bat' and 'cat'. However, they also notice that saying the word 'water' with a sharp 't' sound or a softer 'd'-like sound (as is common in some dialects) does not change the word's core meaning. Which statement best analyzes this observation based on the principles of how speech sounds function in a language?