Alas, I'm not familiar with any variety of Spanish, but that still helps, thank you. Wikipedia has this to say on Greek phonology:
/s/ and /z/ are somewhat retracted ([s̠, z̠]); they are produced in between English alveolars /s, z/ and postalveolars /ʃ, ʒ/. /s/ is variably fronted or further retracted depending on environment, and, in some cases, it may be better described as an advanced postalveolar ([ʃ̟]).
I'll have to look up advanced/retracted consonants, but that at least confirms it's not an issue with TTS or me hearing things. Thanks again!
Nice! Linguistically, I understand that the sigma (in contrast to English s) stresses the teeth a little less and the lips a little more, making it slightly softer and less sibilant. That tends to emphasize the air flow more, introducing a hint of "sh" (or lisp). And I would guess if you give a word more emphasis, you get there by giving it more air, and hence even more "sh".
Whatever classifications and organizations are identified by the linguists, the mouth is capable of an infinite variety within sliding continuities. I would guess that even within Greece, there might be varieties in dialect that would vary a little more in one direction or in another. But dialects themselves are averages, and as you point out, an individual might vary an exact sound according to the need of the moment. I figure, that happens in English; why not in Greek?
Thanks for giving this hint about how native Greeks approach pronunciations! When trying to figure them out from outside, we can get really bogged down in the details (however enlightening they can sometimes be). But I know as a native English speaker that we never begin by analyzing the way we speak. We all picked it up by ear, as infants! So in the long run, to become fluent, we want to acquire this natural ease as well, and (once we get close enough) eventually have to stop thinking about it so hard.
True as to spelling. But the lack in pronunciation is actually a bit of sloppiness or informality. It was once sounded more clearly (quite long ago), but has dropped away. It's rather the same thing with the word mnemonic, where we now sound mostly the n only, although a careful enunciation still calls for both m and n, as the Greeks do. When doubled, the mn passes by very quickly, without intervening vowel sound, so one needs to listen for it more closely than we're generally accustomed to doing these days.
Greek has historic orthography, in ancient Greek η, ι, υ, οι, ει where pronounced with different sounds Now as ee but still written as in old times. Old borrowed words in English are usually from ancient Greek and the
Gr Y; υ is Hy; hy in En: ύμνος/ hymn
Gr Ι; ι is I, i in En: ιδέα/ idea, ιδιώτης/ idiot
Gr Η; η is He; he in En: ήλιος/ Helios
Gr οι is e or oi in En: οικονομία/ economy, Οιδίπους/ Oidipus
Unfortunately the Gr ει is I, i or He in En: εικόνα/ icon, είλωτος/ helot
Greek has historic orthography, ει, η, ι, οι, υ were different sounds in ancient Greek but are now all an ee-sound, written like in Old Greek. Borrowed Greek words which start with HY- start with Υ- in Greek: hymn/ ύμνος, hypnosis/ύπνος (also ordinary sleep), hyper-/ υπερ-, hyperbola/ υπερβολή (also exaggeration), hypothesis/ υπόθεση, hysteria/ υστερία ...
There are 18 forms of the definite article ("the") in its Greek declension: masculine/feminine/neuter gender each having its forms for the nominative, genitive, and accusative cases (there is none in vocative case), and singular/plural for each gender-case pair. ΤΟ is neuter nominative singular, and Ο is masculine nominative singular. See the Tips and Notes for Definite Articles listed when you click on the Basics 1 skill set, beneath its list of lessons. Tips for Basics 2 also has declension and conjugation information you will want to learn and keep referring back to.
Some languages, like Greek, Latin, German, and Russian, inflect their nouns and pronouns in a way that indicates those words' grammatical place or function in the sentence. The set of inflections is called a declension, and a particular inflection is called a case. The nominative case is used for nouns that function as the subject of a sentence (or of a clause), while the accusative is used for the object of a sentence (or clause). A noun that is the object of a prepositional phrase has a case that relates to its preposition, sometimes accusative. (Latin has additional cases - dative and ablative - for such purposes also, and various prepositions each require one or another of those cases.) For example, in the sentence "I am going to the park", the noun park would be inflected according to the use of its preposition "to". The genitive case most often indicates ownership, possession, or belonging. For example, a car has a color, so its color "belongs" to it or with it. In English, we say "the car's color is red", but in languages that use cases (English does not), the word for "car" is inflected, genitive case, to indicate that belonging. English can also use a prepositional phrase to express such a thing: "the voice of the people was heard". In Greek, the noun "people" would not appear in a prepositional phrase, but rather, it would simply appear in the genitive case.
Thus, a declension serves, for a noun or pronoun, a purpose similar to what a conjugation serves for a verb. I / you / he / she / it / we / you / they - eat or drink, and the inflection of the verb, its conjugation, relates to which pronoun (or noun) indicates the subject that does the eating or drinking. It also indicates timing: present, past, future, and more.
English is rather minimalist when it comes to these things, while Greek is considerably more detailed, and that can present complications that English speakers are not accustomed to dealing with in even very simple sentences. It can be a little overwhelming at first. But it's not as difficult as it first appears.
One more thing. Since nouns are declined (inflected), any associated adjectives that modify them are also similarly declined. In Greek, when saying "my red car is dirty", car would be in nominative case, and therefore so would my, red, and dirty. If "my red car ran over the yellow flower", flower would be in accusative case, and therefore so would yellow.
So, coming back to your original question, a definite article (the), or an indefinite one (a/an) for that matter, both occupy the same relationship to a noun that an adjective does. And hence the inflection of the noun is also the inflection used for its article. A feminine noun requires a feminine article, a neuter one, a neuter article, a plural noun, a plural article, a genitive noun, a genitive article. Therefore: το κορίτσι, τα κορίιτσια, ο άντρας, οι άντρες, η γυναίκα, οι γυναίκες.
I hope that helps you in sorting out the whys and wherefores of these language variations.
In very simple terms:
The nominative case is for the subject or anything describing the subject. In "The girl is riding her bike", "the girl" is in the nominative case. In "A cat is a mammal", both "a cat" and "a mammal" are in the nominative case because "to be" is a verb of state and the predicate reflects upon the subject.
The accusative case is for the direct object of a transitive verb. In "The girl is riding her bike", "her bike" is in the accusative case. It is the thing being ridden.
The genitive case is for things like the possessive, but it's more than just the possessive.
English doesn't really mark case very much, which is why we're not very aware of it. It's mostly in the pronouns that we can see nominative vs accusative:
I, he, she, we, they, who
me, him, her, us, them, whom
But other languages, like Greek, overtly mark many noun phrases for case, which inflects not just the noun itself but the articles and adjectives that go with the noun. Another thing Greek has that English does not have is grammatical gender (also called noun classes). This affects the form the different cases take.
none at all, η, ι, υ, ει, οι are all pronounced ee. Greek has historic orthography, in ancient Greek, where all sounds had a unique letter, they were pronounced differently. If a word is borrowed into English one usually can see how the ee-sound should be written if it is η, ι, υ: hymn->ύμνος, gymnastics ->γυμναστική, idea-> ιδέα, hero -> ήρωας.
I think that is something of a dialectical matter, and also what letter follows in the next word, but yes, in many cases a word that ends in sigma is pronounced with a softer, breathier sound, not the hard hiss of the English s, and to us it can come out sounding somewhat like "sh".