AUSTIN, Tex., Nov. 5 (AP) - The Texas Board of Education approved new health textbooks for the state's high schools and middle schools on Friday after the publishers agreed to change wordings in the texts to depict marriage strictly as the union of a man and a woman.

The decision involves two of the biggest textbook publishers and is another example of Texas' exerting its market influence as the nation's second-largest buyer of textbooks. Officials say the decision could affect hundreds of thousands of books in Texas alone.

On Thursday, a board member said that proposed new books ran counter to a Texas law banning the recognition of gay civil unions because the texts used terms like "married partners" instead of "husband and wife."

After hearing the debate on Thursday, one publisher, Holt, Rinehart and Winston, agreed to include a definition of marriage as a "lifelong union between a husband and a wife." The definition, which was added to middle school textbooks, was already in Holt's high school editions, Rick Blake, a company spokesman, said.

The other publisher, Glencoe/McGraw-Hill, changed phrases like "when two people marry" and "partners" to "when a man and a woman marry" and "husbands and wives."

"The board expressed an interest in having us" make the change, Mr. Blake said. "We thought it was a reasonable thing to do."

But Mr. Blake said the publisher did not plan to add its definition of marriage in books to be sold outside Texas. A spokeswoman for Glencoe/McGraw-Hill did not immediately respond to questions.

A list of the books that were approved by the board, as well as those that were not, is sent to school districts for guidance when they choose books.

One board member, Mary Helen Berlanga, a Democrat, asked the panel to approve the books without the changes, but her proposal was rejected on a 10-to-4 vote.

"We're not supposed to make changes at somebody's whim," Ms. Berlanga said. "It's a political agenda, and we're not here to follow a political agenda."

Another board member, Terri Leo, a Republican, said she was pleased with the publishers' changes. She had led the effort to get the publishers to change the texts, objecting to what she called "asexual stealth phrases" like "individuals who marry."

"Marriage has been defined in Texas, so it should also be defined in our health textbooks that we use as marriage between a man and a woman," Ms. Leo said.

Texas legislators enacted a law last year that prohibits the state from recognizing same-sex civil unions. The state already had a ban on gay marriage.

Neither publisher made all the changes that Ms. Leo initially sought. For instance, one passage that was proposed to be added to the teacher's editions read: "Opinions vary on why homosexuals, lesbians and bisexuals as a group are more prone to self-destructive behaviors like depression, illegal drug use and suicide."

Randall Ellis, the executive director of the Lesbian/Gay Rights Lobby of Texas, said the board had overstepped its bounds in suggesting and adopting the new wording.

"Their job is to review for factual information and instead what we see is the insertion of someone's ideology and agenda into the textbook of middle schoolers," Mr. Ellis said.

The board's approval caps months of debate over health textbooks. Much of it had centered on how much sex education should be included.