There are two main ways to pronounce this little word, based largely on what word follows it. If the is followed by a word which begins with a consonant sound (such as water), then it's pronounced \t͟hə\—that is, with the same vowel sound as the word of. However, if the word following it begins with a vowel sound (such as orange), the is usually pronounced \t͟hē\ (to rhyme with me) (but is also sometimes pronounced \t͟hə\, as above).
Is the the most common word in English?
Probably. Vocabulary varies from person to person, and there are likewise differences between the words used in spoken and written language, but the tends to top the list of most commonly used words found in collections of written text.
Can the be trademarked?
It can be attempted, as The Ohio State University tried to do in 2019; the school was unsuccessful in this attempt. The Ohio State was not the first entity to seek a trademark for the word the; clothing designer Marc Jacobs has also asked the patent office for a trademark on this word.
Word History
Etymology
Middle English theo-, from Latin, from Greek the-, theo-, from theos