For example, in the line, "But why thy odour matcheth not thy show," the apostrophe in "thy" creates a sense of closeness and familiarity between the speaker and the reader. The speaker is speaking directly to the reader, as if they are in conversation, and the use of apostrophe helps to convey this sense of intimacy.
The apostrophe also adds intensity to the speaker's message. By contracting the word "why" to "why," the speaker creates a more forceful and emphatic tone. This helps to convey the speaker's sense of urgency and frustration about the subject they are discussing.
Overall, the use of apostrophe in Sonnet 31 helps to create a sense of intimacy and intensity, making the speaker's message feel more personal and impactful.