Arabic teacher Mustafa Alhashimi paces in front of his five adult students, clucking like a turkey. He's illustrating the sound made by the letter qaaf, and his class at the International Language Institute in Northwest Washington is earnestly clucking along with him.

"This is an important letter," Alhashimi says. Qaaf is used in the word Quran, after all, and in Qatar, which is where student Lydia Kepich, a special education teacher, will be going to work in a few months. Unfortunately, neither she nor the rest of the class is quite sure how to pronounce Qatar. A lot of Westerners pronounce it like "gutter," which, Alhashimi emphasizes, is really not nice.

It's the sixth week of this 10-week evening class in beginning Arabic, and the students are still working their way through the 28-letter Arabic alphabet. Some of the sounds the letters make don't have equivalents in English, and they can be difficult for native English speakers to enunciate. Furthermore, the striking letters, with their flourishes, curves, circles and dots, change form depending on where they are in the word. A stand-alone qaaf is what Alhashimi calls a "cup-like shape," beginning with a small circle on the right side with two dots over it. A qaaf that begins a word flattens out on the left. A qaaf in the middle of a word is a small circle with the two dots over it and is linked to the letters before and after it. A qaaf at the end of a word is connected to the letter before it on the right, includes a dotted circle and ends with an upward curve, or cup, on the left.

Alhashimi, 40, insists that all of this is understandable. "Everything about the Arabic language is logic," he assures the class, as he draws the letters on the white board at the front of the small rectangular room. Other than the students' books and notes and Alhashimi's dry-erase lesson, there is nothing remotely Arabic in the room, no place a pupil's wandering eye can land for help; instead, the walls are festooned with reminders about English verb constructions for the daytime ESL students.

Kepich, 30, doesn't have to be here: When she moves to Qatar for her two-year stint, she'll be teaching in English at an international school; she won't have to know Arabic. "But I want to learn it," she says. Her classmates include a French teacher who also conducts tours of Israel, an international development consultant and a Marine, all part of the wave of professionals who see opportunities in knowing Arabic and have helped make it one of the fastest-growing foreign languages in the United States.

Kepich, who has reddish-brown hair pulled back in a ponytail and blue eyes, is paying her own way in this $320 course, and applying herself. She's often one of the first to raise her hand and asks questions at the break. "This is the one who reviewed last class," Alhashimi says of her, when she's the only one who can answer a question.

Alhashimi is a enthusiastic yet stern taskmaster, praising the students when they nail a pronunciation or remember a letter, rebuking them when they don't. "It's not very hard at all," he says, cajoling a discouraged student. "You need to add more chips to your memory," he scolds them all later. And, "My ear is sensitive," he warns. "Listen to Sean. If Sean can make it, you can make it."

Sean Riordan is the star of the class, by virtue of having already picked up a lot of Arabic during more than two years in Kuwait. A 34-year-old Marine Corps major dressed in jeans and flip-flops, he has enrolled in the class to, as he puts it, "get all the things I missed" and because he anticipates a return to the region in his next tour of duty.

Alhashimi is an Iraqi who grew up in Kuwait and emigrated to the United States when he was 25. A computer specialist who is working on his PhD, Alhashimi has a mustache and wears glasses that he occasionally removes toward the end of the intense 21/2-hour class, rubbing his eyes. He started teaching Arabic as a volunteer at his Falls Church mosque, Dar Al Hijrah Islamic Center, helping the children of non-Arab Muslims better understand and appreciate the words from the Quran that they recite every day. Now Alhashimi's students are adults -- members of the military, diplomats, potential translators. He considers teaching Arabic more than a job; it's a labor of love.

"I adore my language," he explains. "I want everyone to know about my language." The more Americans who learn, the better, he adds. "They will be able to communicate with the Arabic world without any mediator or middleman."

The wave of interest in learning Arabic is part of a larger phenomenon in adult education. Americans are signing up for all kinds of foreign language classes, trying to master Chinese, become fluent in Spanish or figure out Farsi. According to a 2002 survey by the Modern Language Association, foreign language study in colleges and universities had jumped by 17 percent over 1998. While the MLA doesn't have any hard data on older language learners, Executive Director Rosemary Feal says that anecdotal evidence indicates that there's been a similar increase in adult study.

That certainly seems to be the case in the Washington area, where institutions from community colleges to private language schools report enrollment surges. While some adults are taking classes for personal enrichment, many, like Kepich and Riordan, believe a second language will open doors for them.

"Career-wise, the Department of Defense has made it clear that gaining and retaining people with languages is a priority," Riordan says. "You have to be able to communicate to be effective."

Adults who want to pursue a second language have many options from which to choose. There are private language schools, such as ILI, which offer arrangements ranging from group classes to one-on-one tutoring sessions. There are courses at universities such as Georgetown or Johns Hopkins. The Graduate School, USDA, which provides continuing education programs open to the general public in three locations in Washington, offered 15 foreign languages this spring, including Czech and Hindi. Even community colleges are getting into the act: Howard Community College is offering its second intensive Arabic institute this summer. And for those who can't make it to class, there are computer software programs sold by companies such as Rosetta Stone, which says it has had a 70 percent compound annual growth rate since 1993.

While Spanish remains the language of choice in the Washington area, students can find instruction in almost any tongue. "You never know" what need is going to crop up in the nation's capital, says Fredrik Skoglund, director of ILI. "We have a guy here five hours a day studying Azeri," before heading to Azerbaijan for the State Department.

Along with perennially popular Spanish and French, Italian, Chinese, Portuguese and Arabic are all in increasing demand. "Spanish is the most requested language in our program," says Klaus Luthardt at the USDA. "Chinese is growing quickly, but not as quickly as Arabic. Arabic has grown more quickly, much more. We have doubled or more than doubled the offerings in the last two, three years." In fact, according to the 2002 MLA survey, enrollment in Arabic grew 92 percent nationwide from 1998 to 2002.

Adults who might think that it's too late to acquire a second language can take heart from recent research. According to a study by linguists Marsha Kaplan and Frederick Jackson of the Foreign Service Institute, "skilled adults learn some aspects of the foreign language better and much faster than children. They can do this because they have learned how to learn." The one area where, experts seem to think, children have the edge is in developing a native-sounding accent, according to the FSI report.

Luthardt of the USDA says he's seen "people who started later in life and learn very well." What it really takes, he says, is dedication and time. "If you're doing a language and you want to get any proficiency at all, this is not a fast process," says Luthardt. "You'll be taking a good number of courses. Think of it as a marathon run. It's not a sprint."

So how much time are we talking about? Well, it depends on the language. The State Department divides languages into three categories of difficulty. The first category includes languages that are closely related to English, such as Spanish or French. It is estimated that such a language would take a half-year of study to attain "general professional proficiency." The second category includes languages that differ significantly -- linguistically or culturally -- from English. Think Greek, Russian, Vietnamese. They would take a full year. Finally, there are four languages considered "exceptionally difficult" for native English speakers to master. For these four -- Arabic, Chinese, Japanese and Korean -- it would take two years of study to achieve proficiency, with the second year of study occurring in the foreign country.

There are some things students can do to make their studies more effective. The Foreign Service authors found that class sizes of five to six for beginners and three to four for advanced levels and more difficult languages are best. Learning strictly through one-on-one tutorial can be a detriment, because students need the interaction with classmates. But perhaps the most important element is the teacher.

"You want someone who is patient, somebody who is able to explain the structures when you ask about them and who keeps you engaged," says Luthardt. Students also must be comfortable around their teachers. "If you're going to be afraid of making mistakes, you're going to be silent for a long time," he says. "A really good language teacher makes it so the mistakes don't matter in the sense that you don't feel bad about them, you learn from them."

Lydia Kepich clearly doesn't mind trying things out in class and likes Alhashimi's approach to teaching. She appreciates the insights he gives his students into the culture behind the language, citing his lesson about the Arabic word for "friend." In Arabic, the word for "friend" comes from the root "truth," because, he told the class, "Who is your friend? The one who tells you the truth."

Friends had told Kepich that she might learn to speak Arabic but never to write it. But she says Alhashimi insists that's not true, and he's made her a believer.

Degrees of Difficulty

Just how long it takes to master a new language at the Foreign Serivice Institute.

Category 1: Languages most like English

French, Italian, Portuguese, Romanian, Spanish, Swedish, Dutch, Norwegian, Afrikaans, etc.

Weeks to Achieve Goal: 24

Class Hours to Achieve Goal: 600

Category 2: Languages with significant differences from English

Albanian, Amharic, Azerbaijai, Bulgarian, Finnish, Greek, Hebrew, Hindi, Hungarian, Icelandic, Khmer, Latvian, Nepali, Polish, Russian, Serbian, Tagalog, Thai, Turkish, Urdu, Vietnamese, Zulu, etc.

Weeks to Achieve Goal: 44

Class Hours to Achieve Goal: 1,100

Caegory 3: Languages that are exceptionally difficult for native English speakers

Arabic, Chinese, Japanese and Korean

Weeks to Achieve Goal: 88*

Class Hours to Achieve Goal: 2,200

SOURCE: State Department | * Second year is in the country

Elizabeth Chang, a Magazine copy editor, writes regularly for The Post.