But Christians, who make up 10 percent of the country’s population, say the Allah ban is one of many signs that a conservative Islamic movement is steering an increasingly intolerant government policy.

In recent weeks, the religious authorities have banned Muslims from taking part in Halloween and scolded them for petting dogs, which the state Islamic authorities view as unclean.

The government’s Department of Islamic Development did not respond to a request to explain the official position on the Allah ban, but over the years the government has offered a number of reasons.

When the government first prohibited the “printing, publication, sale, issue, circulation or possession” of Malay-language Bibles in 1981, it said the books were “prejudicial to the national interest and security” of the country.

Islamic authorities have warned that Malay-language Bibles could be used for proselytizing Muslims, which is illegal in Malaysia.

The Department of Islamic Development argues that Allah is not a generic name for God but signifies “the religion of the person who uses it.”

“That is the reason why the usage needs to be monitored and preserved by the government in order to ensure that no one will be confused with the Most Exalted name,” the department says on its website.

Perhaps more than at any time in recent decades, Malaysia’s moderate voices are sounding an alarm.

Zainah Anwar, the founder of Sisters in Islam, a women’s rights group, describes a “headlong descent into a puritanical, extremist, intolerant brand of Islam in this country.”

“Malaysia’s moderate Islam is only touted for Western consumption,” she wrote in The Star newspaper on Sunday. “For too long this government has given almost a carte blanche to the religious authorities and the belligerent supremacists to take the lead and define what Islam is and is not.”

Enforcement is patchy for the Allah rule, which has been promulgated in different forms and by different government and religious authorities over the past three decades. But the rule has been upheld by the country’s highest courts.

Islamic scholars say banning non-Muslims from using “Allah” is unique to Malaysia.

“You can’t find this idea in any previous Islamic discourse,” said Yahya Cholil Staquf, a senior cleric at Nahdlatul Ulama, the largest Islamic organization in Indonesia, Malaysia’s neighbor and the world’s most populous Muslim-majority country. “Every language has its own word for God. Allah is just a word to acknowledge God. It’s not a word for only Muslims.”

The Christian minority in Indonesia, where the lingua franca is similar to Malaysia’s, refers to God as Allah without any controversy; Indonesian Bibles are often imported into Malaysia, when they are not seized by the authorities.

On Tuesday, a court in Kuala Lumpur, the Malaysian capital, is scheduled to begin deliberations in a long-running case over the seizure in 2007 of a box of Sunday school materials, including coloring books and Bible story books, that used the word Allah.

The books were eventually returned, but their owner, a large evangelical Christian denomination, Sidang Injil Borneo, is challenging the constitutionality of the seizure because such confiscations continue. Malaysian customs agents seized compact discs and books destined for a Borneo church in late October.

Minorities need clarity on freedom of religion in the country, said the Rev. Jerry Dusing, the church president.

“No law can prohibit anyone from the reasonable practice of their faith,” he said in an interview. “Why on earth are they banning words?”

The Roman Catholic church has also been embroiled in a court case challenging Malaysia’s Allah ban after the government ordered that its newsletter, The Herald, stop using Allah.

When a judge ruled in the church’s favor in 2009, 10 churches were vandalized, one gutted by fire. An appeals court overturned the ruling last year.

“It is our common finding that the name Allah was not an integral part of the Christian faith and practice,” the lead judge, Mohamed Apandi Ali, said.

An appeal was rejected, but church leaders are trying to get the decision reviewed.

Like Christianity, Islam was also introduced here by foreigners. Centuries before European colonists arrived in Asia, Arab traders spread Islam and Arab culture here, infusing the Malay language with words such as Allah. Christianity came later, with the arrival of missionaries from the West and European colonialism.

Islam is the official religion of Malaysia, and Muslims are governed by Shariah, though Christians, Hindus and Buddhists make up sizable minorities.

The United Malays National Organization, or UMNO, has been the dominant party of the coalition in power for 57 years, but the group was nearly toppled by a multiethnic coalition of parties last year.

“The more Muslims feel they are under threat, the more UMNO can maintain its political hegemony,” Mr. Wan Saiful said.

Mr. Wan Saiful says Malaysia’s conservative Muslims are disconnected from the wider Islamic world. Arabic-language bibles used by Christians in countries such as Egypt and Lebanon use the word Allah for God.

He was attending a conference overseas this year when the court affirmed the ban on the Catholic church using Allah in its newsletter.

“This Palestinian guy came up to me and said, ‘The world is laughing at you. I’m from an Arab country and everyone uses the word, every day.'”