Thanks for your question.
Greek ‘hagios’ - properly, different (unlike), other ("otherness"), holy; for the believer, (hágios) means "likeness of nature with the Lord" because "different from the world."
Saint is used in the New Testament to describe those who have believed the gospel, been baptised into Christ for the remission of their sins, and are making a determined effort to live by the commandments of Christ.
Ephesians 2:11 Wherefore remember, that ye being in time past Gentiles in the flesh, who are called Uncircumcision by that which is called the Circumcision in the flesh made by hands; 12 That at that time ye were without Christ, being aliens from the commonwealth of Israel, and strangers from the covenants of promise, having no hope, and without God in the world: 13 But now in Christ Jesus ye who sometimes were far off are made nigh by the blood of Christ. 14 For he is our peace, who hath made both one, and hath broken down the middle wall of partition between us; 15 Having abolished in his flesh the enmity, even the law of commandments contained in ordinances; for to make in himself of twain one new man, so making peace; 16 And that he might reconcile both unto God in one body by the cross, having slain the enmity thereby: 17 And came and preached peace to you which were afar off, and to them that were nigh. 18 For through him we both have access by one Spirit unto the Father. 19 Now therefore ye are no more strangers and foreigners, but fellowcitizens with the saints, and of the household of God; 20 And are built upon the foundation of the apostles and prophets, Jesus Christ himself being the chief corner stone;
Baptised into Christ our behaviour must change.
Ephesians 5:1 Be ye therefore followers of God, as dear children; 2 And walk in love, as Christ also hath loved us, and hath given himself for us an offering and a sacrifice to God for a sweetsmelling savour. 3 But fornication, and all uncleanness, or covetousness, let it not be once named among you, as becometh saints; 4 Neither filthiness, nor foolish talking, nor jesting, which are not convenient: but rather giving of thanks. 5 For this ye know, that no whoremonger, nor unclean person, nor covetous man, who is an idolater, hath any inheritance in the kingdom of Christ and of God.
The members of the ecclesia in Ephesus are called saints
Ephesians 1:1 Paul, an apostle of Jesus Christ by the will of God, to the saints which are at Ephesus, and to the faithful in Christ Jesus:
Similarly those at Philippi, Colosse and Rome
Philippians 1:1 Paul and Timotheus, the servants of Jesus Christ, to all the saints in Christ Jesus which are at Philippi, with the bishops and deacons:
Philippians 4:21 Salute every saint in Christ Jesus. The brethren which are with me greet you. 22 All the saints salute you, chiefly they that are of Caesar's household.
Colossians 1:1 Paul, an apostle of Jesus Christ by the will of God, and Timotheus our brother, 2 To the saints and faithful brethren in Christ which are at Colosse: Grace be unto you, and peace, from God our Father and the Lord Jesus Christ.
Colossians 1:26 Even the mystery which hath been hid from ages and from generations, but now is made manifest to his saints: 27 To whom God would make known what is the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory: 28 Whom we preach, warning every man, and teaching every man in all wisdom; that we may present every man perfect in Christ Jesus:
Jude’s general epistle is directed to saints
Jude 1:1 Jude, the servant of Jesus Christ, and brother of James, to them that are sanctified by God the Father, and preserved in Jesus Christ, and called: 2 Mercy unto you, and peace, and love, be multiplied. 3 Beloved, when I gave all diligence to write unto you of the common salvation, it was needful for me to write unto you, and exhort you that ye should earnestly contend for the faith which was once delivered unto the saints.
The ‘world’ is generally presented as unholy and at enmity with God through sin.
The ‘care of this world’ is dangerous to those who would be saints
Matthew 13:22 He also that received seed among the thorns is he that heareth the word; and the care of this world, and the deceitfulness of riches, choke the word, and he becometh unfruitful.
The ‘world’ is opposed to God and antagonistic to saints
John 15:17 These things I command you, that ye love one another. 18 If the world hate you, ye know that it hated me before it hated you. 19 If ye were of the world, the world would love his own: but because ye are not of the world, but I have chosen you out of the world, therefore the world hateth you.
John 17:25 O righteous Father, the world hath not known thee: but I have known thee, and these have known that thou hast sent me.
Colossians 2:8 Beware lest any man spoil you through philosophy and vain deceit, after the tradition of men, after the rudiments of the world, and not after Christ.
The ‘world’ is guilty in the sight of God
Romans 3:19 Now we know that what things soever the law saith, it saith to them who are under the law: that every mouth may be stopped, and all the world may become guilty before God.
Those who would be saints must not be conformed to this world.
Romans 12:2 And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God.
1 Corinthians 1:20 Where is the wise? where is the scribe? where is the disputer of this world? hath not God made foolish the wisdom of this world? 21 For after that in the wisdom of God the world by wisdom knew not God, it pleased God by the foolishness of preaching to save them that believe.
Christ’s sacrifice was in order to deliver us from this world
Galatians 1:4 Who gave himself for our sins, that he might deliver us from this present evil world, according to the will of God and our Father
Those who believe the gospel and are baptised into Christ are ‘dead’ to this world
Colossians 2:20 Wherefore if ye be dead with Christ from the rudiments of the world, why, as though living in the world, are ye subject to ordinances, 21 (Touch not; taste not; handle not; 22 Which all are to perish with the using;) after the commandments and doctrines of men?
Worldly lusts are to be denied
1 John 2:15 Love not the world, neither the things that are in the world. If any man love the world, the love of the Father is not in him. 16 For all that is in the world, the lust of the flesh, and the lust of the eyes, and the pride of life, is not of the Father, but is of the world. 17 And the world passeth away, and the lust thereof: but he that doeth the will of God abideth for ever.
Titus 2:11 For the grace of God that bringeth salvation hath appeared to all men, 12 Teaching us that, denying ungodliness and worldly lusts, we should live soberly, righteously, and godly, in this present world;
James 1:27 Pure religion and undefiled before God and the Father is this, To visit the fatherless and widows in their affliction, and to keep himself unspotted from the world.
Friendship with this world puts us at enmity with God
James 4:4 Ye adulterers and adulteresses, know ye not that the friendship of the world is enmity with God? whosoever therefore will be a friend of the world is the enemy of God.
When Christ returns he will judge the world
Acts 17:31 Because he hath appointed a day, in the which he will judge the world in righteousness by that man whom he hath ordained; whereof he hath given assurance unto all men , in that he hath raised him from the dead.
Those in Christ will overcome the world
2 Peter 1:4 Whereby are given unto us exceeding great and precious promises: that by these ye might be partakers of the divine nature, having escaped the corruption that is in the world through lust.
1 John 5:5 Who is he that overcometh the world, but he that believeth that Jesus is the Son of God?
In conclusion the difference between the saints and the world is one of behaviour. Those ‘in the world’ live to satisfy their own desires, but the saints ‘in Christ’ live by his commandments.
I hope you have found this helpful.