Lithuanian language belongs to Baltic group of the Indo-European languages. The only other Baltic language is Latvian. Since the 19th century, numerous linguists regard Lithuanian language as the purest surviving Indo-European language which is least changed by outside influences.
History of the Lithuanian language
A couple thousand years ago Baltic languages were spoken in a much larger area, covering also large areas of today's Poland, Russia and Belarus. This area shrunk due to Slavic expansion and also due to the Germanic crusades that have destroyed the Old Prussian language. The Baltic area continued to shrink in 15th-19th centuries as the Baltic languages, including Lithuanian, continued to be spoken mainly by peasants whereas the nobility switched to German or Polish (depending on location), regarded to be more prestigious.
The 19th century National Revival restored the prestige of speaking the Baltic languages. Peaceful resistance defended the language under Russian Imperial occupation when it was forbidden to print Lithuanian or to speak Lithuanian in public. A secret book smuggler network was established (recognized as unique by UNESCO) which illegally imported Lithuanian books and press from Germany. Under the influence of linguist Jonas Jablonskis the language was purified by replacing Slavic loanwords with neologisms and establishing the modern orthography. Due to this reason, 19th century Lithuanian differs more from modern Lithuanian than English of the era does differ from the modern English. However, several centuries old Lithuanian is still intelligible for a modern person.
The culmination of national revival was the 1918 declaration of Lithuanian independence, although the language had to survive another onslaught of Russification under the Soviet occupations of 1940-1941 and 1944-1990.
Since the 19th century Lithuanian language is regarded by many to be the primary definition of who is Lithuanian and who isn't. The importance of language in defining ethnicity is therefore much greater than in Britain or the USA where a person can easily be regarded to be Irish (for example) even if his native language is not Irish.
The Lithuanian language situation today
Today Lithuanian is the sole official language in Lithuania and while there are official areas where ethnic minorities may use their own languages (for instance as the medium of instruction in their public schools), the position of Lithuanian as a language for interethnic communication strengthened over the time since 1990. It remains to be seen whether this will be true in the future as English have displaced Lithuanian from many trademarks in the main cities and English slang entered the conversations.
The Lithuanian language commission which regulates the language takes a moderate stance on language purism. Unlike Icelandic, it allows new loanwords (and Lithuanian has many older loanwords). But it often attempts to coin neologisms for new terms, with mixed success. E.g. "Spausdintuvas" (from "spausdinti" - "to print") displaced "Printeris" as the Lithuanian name for a printer, but "Skaitlys" failed to displace "Skaneris" (scanner) in popular speech.
Despite over a million of Lithuanians emigrating since the 19th century the emigrant communities typically loose the language over some three generations as nowhere do the Lithuanians make a majority and therefore they form mixed families with other linguistic groups. Currently, there are the largest overseas Lithuanian-speaking communities in the United States, United Kingdom, Ireland, Norway and Spain. Some historical Lithuanian communities "on the wrong side of the state boundary" have been more successful at preserving the language, namely the Punsk/Punskas community in Poland where Lithuanian language schools exist and Lithuanians make the majority of the population in some towns.
In addition to standard Lithuanian, there are dialects somewhat corresponding to the ethnographic regions. Discouraged under the Soviet occupation as "tongue of the uneducated" and thus heavily declined in use, the dialects recently earned some respect. Samogitian dialect (so unique it is sometimes called a language) is even used on some local signs.
Lithuanian alphabet, orthography and spelling
Lithuanian is written in the Latin script, but compared to English Lithuanian has 9 additional letters (Ą, Č, Ę, Ė, Į, Š, Ų, Ū, Ž) and lacks 3 (W, Q, X). Unlike English the Lithuanian spelling is very regular, meaning the words are almost always pronounced as they are written, and most letters have only one possible way to pronounce them. "A" is always pronounced as in the English word "Barn", "I" is pronounced as in "Ship", "E" is pronounced as in "Get", "O" as in "Glory" and "U" as in "Pull".
The additional Lithuanian vowels sound similarly to their ordinary counterparts, but must be pronounced longer (e.g. "Ū" and "Ų" are both relatively similar to a long "U"). The only exception is "Ė". The additional consonants sound the following: "Č" is like "Ch" in "Charm", "Š" is like "Sh" in "Ship" and "Ž" is like "S" in "Measure". Unlike English Lithuanian has only one digraph and that is "Ch", pronounced as "Kh" in "Khan".
The exact pronunciation of several Lithuanian letters differs from their English counterparts. Lithuanian "J" is like "Y" in English while Lithuanian "Y" is like "ee" in "sheep".
Lithuanian is a synthetic language, meaning that the same word takes different forms when it is used in different contexts. This eradicates the need for grammatical particles. What is said in English in 2, 3 or even 4 words often may be said in Lithuanian using just a single word. For instance "I will come" is "Ateisiu" in Lithuanian, "You will come" is "Ateisi", "I did come" is "Atėjau", "He/she used to come" - "Ateidavo" and so on.
The changes a word takes in different situations can be predicted, as there are only several different versions of these changes. For instance, every noun that ends with "as" would end with "o" in circumstances when in English particle "of" would be used. E.g. the name "Jonas" (John) would change to "Jono" (of John) in this case and to "Jonui" if you would want to say "for John". Similarly "Kaunas" (name of the second largest city of Lithuania) would change to "Kauno" and "Kaunui" in these cases ("of Kaunas", "for Kaunas" respectively). Therefore you don't need to learn every form of every word to learn Lithuanian - you only need to learn the main forms and the basic rules for creating the other forms.
Due to this nature of Lithuanian language, it is common to add Lithuanian endings to foreign names and placenames when speaking in Lithuanian. Without doing this the language would become ambigous. Therefore "London" in Lithuanian is "Londonas", and it can be referred to as Londono, Londonui, Londoną, Londonu, Londone, Londonan or Londonai, depending on what exactly has to be said about the city. Traditionally the orthography of foreign personal names is also Lituanized, but this is now getting rarer, with many (though not all) daily newspapers dropping this practice. Therefore now you are more likely to encounter George'as Bushas than Džordžas Bušas as the name of the former US president. One exception is works of fiction where the character names are almost always transliterated into Lithuanian orthography (e.g. "Don Kichotas" instead of "Don Quixote").
There are 7 cases (and 2 additional rarely used ones) of the nouns in the Lithuanian language. The verbs have only 4 tenses, however. There is singular and plural. Unlike in English (but like in most other languages) there are genders, with each word being either masculine or feminine.
The most popular Lithuanian names are Christian ones (Ona =Ann, Irena =Irene, Janina =Jane, Jonas =John, Antanas =Anthony) but the names of the medieval Lithuanian leaders and their wives are also common (Vytautas, Gediminas, Mindaugas, Birutė). Moreover, some ordinary words are today used as names (e.g. Rasa =Dew).
Due to differences in masculine and feminine endings, there are no "universal names" which could be used for both males and females. Female Lithuanian names end in "-ė" or "-a" while most male names end in "-as", "-is" or "-us".
The endings of male and female surnames likewise differ. Furthermore, every female surname has 3 variants: one for an unmarried girl (ending by -aitė, -ytė, -ūtė or -utė), one for a married woman (-ienė) and one optional marriage-neutral, introduced in the 2000s per a European Union request (-ė).
Some ethnic minority people (especially the more assimilated ones) eventually add Lithuanian endings to their names, even if the names remain non-Lithuanian, e.g. an ethnic Russian citizen of Lithuania named "Ivan Ivanov" may alter his name to "Ivanas Ivanovas" or at least "Ivanas Ivanov".
Lithuanian words and phrases
You may find some of the common Lithuanian words, including mp3 files with their spellings, at the Omniglot website.