forces and warfare 360 Social problems and social services 360 Social problems and services; associations 361 Social problems and services 362 Social problems of and services to groups of people 363 Other social problems and services 364 Criminology 365 Penal and related institutions 366 Secret associations and societies 367 General clubs 368 Insurance 369 Associations 370 Education 370 Education 371 Schools and their activities, special education 372 Primary education (elementary education) 373 Secondary education 374 Adult education 375 Curricula 376 No longer used — formerly "Education of women" 377 No longer used — formerly "Ethical education" 378 Higher education (Tertiary education) 379 Public policy issues in education 380 Commerce, communications and transportation 380 Commerce, communications transportation 381 Commerce (Trade) 382 International commerce (Foreign trade) 383 Postal communication 384 Communications 385 Railroad transportation 386 Inland waterway and ferry transportation 387 Water, air, space transportation 388 Transportation 389 Metrology and standardization 390 Customs, etiquette and folklore 390 Customs, etiquette, folklore 391 Costume and personal appearance 392 Customs of life cycle and domestic life 393 Death customs 394 General customs 395 Etiquette (Manners) 396 No longer used — formerly "Women's position and treatment" 397 No longer used — formerly "outcast studies" 398 Folklore 399 Customs of war and diplomacy Class 400 – Language 400 Language 400 Language 401 Philosophy and theory, international languages 402 Miscellany 403 Dictionaries, encyclopedias, concordances 404 Special topics of language 405 Serial publications 406 Organizations and management 407 Education, research, related topics 408 Groups of people 409 Geographic treatment and biography 410 Linguistics 410 Linguistics 411 Writing systems of standard forms of languages 412 Etymology of standard forms of languages 413 Dictionaries of standard forms of languages 414 Phonology and phonetics of standard forms of languages 415 Grammar of standard forms of languages 416 No longer used — formerly "Prosody" 417 Dialectology and historical linguistics 418 Standard usage (Prescriptive linguistics) 419 Sign languages 420 English and Old English languages 420 English and Old English (Anglo-Saxon) 421 Writing system, phonology, phonetics of standard English 422 Etymology of standard English 423 Dictionaries of standard English 424 No longer used — formerly "English thesauruses" 425 Grammar of standard English 426 No longer used — formerly "English prosodies" 427 Historical and geographical variations, modern nongeographic variations of English 428 Standard English usage (Prescriptive linguistics) 429 Old English (Anglo-Saxon) 430 German and related languages 430 German and related languages 431 Writing systems, phonology, phonetics