What does the statement thereto I plight thee my troth in traditional wedding vows mean?

The phrase "thereto I plight thee my troth" is an archaic way of saying "to that (the marriage) I pledge you my loyalty" or "to that (the marriage) I promise you my faithfulness." It's a very old-fashioned way of expressing the commitment to the marriage vows.

Here's a breakdown:

* Thereto: This refers to the marriage itself, the act of being joined as husband and wife.

* Plight: This means to pledge or promise solemnly.

* Thee: This is the old-fashioned word for "you."

* Troth: This means faithfulness, loyalty, and commitment.

So, the entire phrase essentially means, "I pledge to you my faithfulness and loyalty in this marriage."

This phrasing is rarely used in modern wedding vows, but it reflects the historic emphasis on the sacredness and enduring nature of marriage.