Unlike English, which uses word order and prepositions to express the grammatical function of nouns in a sentence, Classical Slith used declensions, modifying the endings of the nouns. The result of this was that the words could go in nearly any order and still be understood, which is a feat that is difficult to accomplish in English.

Classical Slith had seven cases: nominative, genitive, dative, accusative, instrumental, locative, and vocative. Each one is represented in two numbers: singular and plural.

The uses listed here are the basic uses. Other uses of the cases will be detailed elsewhere with the constructions.

For clarification: this stage of the slith tongue did not have articles. That is, it had no words for "the," "a," or "an." When translating into English, I have inserted them wherever they make sense.

Classical Slith has three genders: masculine, feminine, and neuter. Gender is grammatical, which means that most words have assigned genders that may or may not have anything to do with their meanings. Gender is extremely easy to spot, because it is expressed with the vowel that comes right after the stem of the word: -o is masculine, -a is feminine, and -e and i (as well as nothing at all) are neuter. Examples: ksevoss is masculine; mōra is feminine; perēn is neuter; Thkhi is neuter; and rhes is neuter.

Early in Archaic Slith, the gender of the noun actually related to its meaning, and many of these nouns are left over from that period (ksevoss, meaning "[manly] male slith," is one obvious example). However, for many nouns, the gender is simply arbitrary. Many nouns also have flexible gender: ksevoss refers to a male slith, and kseva refers to a female.

Note that nouns with stems ending in a consonant, such as Calindōr, add epenthetic (or technically euphonic) vowels between the stem and the case ending for ease of pronunciation. These nouns alternate between I and E epenthetics, and each form must be learned individually, although the vowel tends to match a final vowel if one is present in the case ending, as Calindorithi.

Note also that the gender vowel is not completely constant with respect to length. For most declensional patterns, the only way to tell the difference in writing between a locative singular and an instrumental plural is by the length of the gender vowel (long is locative singular, short is instrumental plural). In speech, the normal laws of stress also cause a differentiation: the locative singular is stressed on the penult, and the instrumental plural is stressed on the antepenult. In addition, the neuter vowel-stems lengthen their gender vowels in many of the oblique cases (as kālēt).

The nominative is used for the subject of a sentence. Example 1: "The man walks" is Ksevoss bainath. (Note: from now on, I will simply translate ksevoss as "man," under the assumption that we're talking about sliths here.) The nominative is also used for the complement of a linking verb, such as the verb "to be." Example 2: "This is a man" is Leikhoss bitath ksevoss.

The form of the singular is the base form of the noun. It ends in -ss for masculine nouns and essentially a zero ending (nothing at all) for all others. Consonant-stems (such as Calindōr) lengthen the vowel in the final syllable in order to distinguish the nominative from the vocative. Stems ending in a stop always mutate to a fricative in the nominative (as, for example, ferekh). Feminine: Thassaka. Masculine: Pithoss. Neuters: kāle, Thkhi, Calindōr (stem: Calindor-), ferēkh (stem ferekt-).

The plural involves adding an -i. Feminine: Thassakai. Masculine: Pithoi. Neuters: kālei, Thkhī, Calindori, ferekti. Note that neuter I-stems lengthen the vowel, because they can't add another letter.

The genitive is used for just about anything that can be expressed using the word "of" in English. Its primary use is to indicate possession. Example 1: "the man's speech" is ksevose hessoss. It also is used to express a partitive concept. Example 2: "a flagon of ale" is kālīs fērletke. (This is clearly not possession, because "an ale's flagon" doesn't mean quite the same thing.)

The form of the singular involves a suffix of an -e. Feminine: Thassakase. Masculine: Pithose. Neuters: kālē, Thkhie, Calindore, ferekte. Note that neuter E-stems lengthen the E, rather than adding another letter.

The plural is formed with a -rhōm suffix. Feminine: Thassakarhōm. Masculine: Pithorhōm. Neuters: kālerhōm, Thkhirhōm, Calindorerhōm, ferekterhōm. Consonant-stem neuters prefer the e epenthetical here.

The dative is used for most things that "to" or "for" prepositional phrases express in English. It is used for the indirect object of the verb. Example 1: "I spoke to the man" is ksevothi hessom. It is also used to express that something was done on behalf of someone else. Example 2: "I did this for the man" is ksevothi leikhon fakhom.

The form of the singular involves a suffix of a -thi. Feminine: Thassakathi. Masculine: Pithothi. Neuters: kālethi, Thkhithi, Calindorithi, ferektithi. Consonant-stem neuters prefer the i epenthetical here.

The plural is formed with an -is suffix. Feminine: Thassakais. Masculine: Pithois. Neuters: kāleis, Thkhīs, Calindoris, ferektis. As usual, I-stems lengthen the vowel, because they cannot add another I.

The accusative is used for the direct object of a verb. Example 1: "I see the man" is ksevon vīdam.

The form of the singular involves a suffix of a nasal consonant. Feminine: Thassakam. Masculine: Pithon. Neuters: kālem, Thkhin, Calindorem, ferektem. Consonant-stem neuters prefer the e epenthetical here.

The plural is formed with a -kh suffix. Feminine: Thassakakh. Masculine: Pithokh. Neuters: kālēkh, Thkhīkh, Calindorekh, ferektekh. Consonant-stem neuters prefer the e epenthetical here.

The instrumental is used to express the means by which something is done. This normally is conveyed with "by" or "with" in English. Example 1: "I killed the man with a spear" is ksevon fālaktet khthōrom.

The form of the singular involves adding a -t. Feminine: Thassakat. Masculine: Pithot. Neuters: kālēt, Thkhīt, Calindoret, ferektet. Consonant-stem neuters prefer the e epenthetical here.

The plural is formed by adding a -ni. Feminine: Thassakani. Masculine: Pithoni. Neuters: kāleni, Thkhini, Calindoreni, ferekteni. Consonant-stem neuters prefer the e epenthetical here. Note also that the gender vowels are all short, in order to differentiate between this case and the locative singular.

The locative is used to express the place where something is happening. A locative by itself just indicates a general proximity to a place, which may (from context) be construed with several different prepositions. Example 1: "I was walking on the mountain is mōrāni bainakhom. Example 2: "I spoke in Bahssikava" is Bassikāvāni hessom. Example 3: "I am at home is dōmini bitam. If one wants to represent a more exact relationship with a location ("I am on top of the house," for example), one must use a preposition.

The form of the singular involves adding a -ni. Feminine: Thassakāni. Masculine: Pithōni. Neuters: kālēni, Thkhīni, Calindorini, ferektini. Consonant-stem neuters prefer the i epenthetical here. Note also that the gender vowels are all (except the epentheticals) long, in order to differentiate between this case and the instrumental plural.

The plural is formed by adding a -khi. Feminine: Thassakakhi. Masculine: Pithokhi. Neuters: kālekhi, Thkhikhi, Calindorikhi, ferektikhi. Consonant-stem neuters prefer the i epenthetical here.

The vocative is used for a direct address of someone or something. Generally it has the feel of calling out to a person. Example 1: "Pithoss, speak" is Pithos, hessaes.

The form of the singular involves some kind of shortening, for the most part. Feminine: Thassakā. Masculine: Pithos. Neuters: kāl, Thkh, Calindor, ferekh. Consonant-stem neuters shorten the vowel that was lengthened in the nominative and retain any final-consonant mutation.

The plural is identical to the nominative plural.

Adjectives in the classical tongue decline almost identically to the way that nouns do. A few simple rules govern their behavior.

• Rule 1: Adjectives are marked by long vowels in almost all cases, which distinguishes them from nouns.
  • Example 1: Kālōs is an adjective, and Pithoss is a noun, which one can see from the fact that kālōs has a long gender vowel and Pithoss a short one.
  • Exception 1a: Neuter adjectives have the same forms as nouns. See Rule 2.
  • Exception 1b: Adjectives have the same long-short dichotomy between the locative singular and the instrumental plural; kālōni is locative singular, and kāloni is instrumental plural.
  • Exception 1c: The vocative is never long, ranging from short feminine kālas and masculine kālos to zero-grade neuter kāl.
• Rule 2: Neuter adjectives take the E-stem forms.
• Example 2a: "The noble thing" is kāle.
• Example 2b: "He did the noble thing" is kālem fakhoth.
• Rule 3: Substantive adjectives (that is, adjectives being used as nouns) take the same forms as nouns; that is, they have short vowels in the appropriate places. Since they have gender, it is often useful to insert in English a dummy noun of the appropriate type: "man" for masculine, "woman" for feminine, and "thing" for neuter.
• Example 3a: "The noble man" is simply kāloss. The functions as a noun in every way: "The noble man speaks" is kāloss hessath.
• Example 3b: Since any adjectival word can be made substantive, a participle can be, too: "The walking man" is bainathoss (cf. bainathōs, "walking").
• Exception 3: Neuter substantive adjectives take the I-stem forms: "the thing that was spoken" ("the spoken thing") is hessoki.

Note: All E-stem words native to Classical Slith are adjectives. Some earlier, later, or foreign words are also E-stem in form, so they decline like E-stems, but these are considered irregular. The name of the Bahssikavan, Legare, is one example of a later E-stem word.